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 $164.79   10.826%   $182.6302   $182.63   $182.65   $182.60  
  Purchase #2 $219.40   6.510%   $233.6829   $233.68   $233.70   $233.70  
  Purchase #3 $148.63   12.206%   $166.7718   $166.77   $166.75   $166.80  
  Purchase #4 $72.96   5.343%   $76.8583   $76.86   $76.85   $76.90  
  Purchase #5 $235.48   10.280%   $259.6873   $259.69   $259.70   $259.70  
  Purchase #6 $156.61   11.591%   $174.7627   $174.76   $174.75   $174.80  
  Purchase #7 $112.98   6.442%   $120.2582   $120.26   $120.25   $120.30  
  7 purchase totals = $1,110.85       $1,214.6514   $1,214.65   $1,214.65   $1,214.80