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 $85.62   10.426%   $94.5467   $94.55   $94.55   $94.50  
  Purchase #2 $156.86   4.315%   $163.6285   $163.63   $163.65   $163.60  
  Purchase #3 $55.62   12.103%   $62.3517   $62.35   $62.35   $62.40  
  Purchase #4 $230.95   10.812%   $255.9203   $255.92   $255.90   $255.90  
  Purchase #5 $193.88   12.184%   $217.5023   $217.50   $217.50   $217.50  
  Purchase #6 $210.82   7.297%   $226.2035   $226.20   $226.20   $226.20  
  Purchase #7 $227.99   8.705%   $247.8365   $247.84   $247.85   $247.80  
  7 purchase totals = $1,161.74       $1,267.9895   $1,267.99   $1,268.00   $1,267.90