Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $168.38   8.461%   $182.6266   $182.63   $182.65   $182.60  
  Purchase #2 $173.45   8.872%   $188.8385   $188.84   $188.85   $188.80  
  Purchase #3 $243.61   7.518%   $261.9246   $261.92   $261.90   $261.90  
  Purchase #4 $92.53   12.309%   $103.9195   $103.92   $103.90   $103.90  
  Purchase #5 $179.46   8.409%   $194.5508   $194.55   $194.55   $194.60  
  Purchase #6 $214.93   10.828%   $238.2026   $238.20   $238.20   $238.20  
  Purchase #7 $206.90   9.223%   $225.9824   $225.98   $226.00   $226.00  
  7 purchase totals = $1,279.26       $1,396.0450   $1,396.04   $1,396.05   $1,396.00