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 $58.82   7.486%   $63.2233   $63.22   $63.20   $63.20  
  Purchase #2 $179.42   9.102%   $195.7508   $195.75   $195.75   $195.80  
  Purchase #3 $237.39   3.628%   $246.0025   $246.00   $246.00   $246.00  
  Purchase #4 $197.97   10.484%   $218.7252   $218.73   $218.75   $218.70  
  Purchase #5 $166.65   9.205%   $181.9901   $181.99   $182.00   $182.00  
  Purchase #6 $248.94   10.725%   $275.6388   $275.64   $275.65   $275.60  
  Purchase #7 $86.98   12.224%   $97.6124   $97.61   $97.60   $97.60  
  7 purchase totals = $1,176.17       $1,278.9431   $1,278.94   $1,278.95   $1,278.90