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 $62.94   3.411%   $65.0869   $65.09   $65.10   $65.10  
  Purchase #2 $234.84   13.684%   $266.9755   $266.98   $267.00   $267.00  
  Purchase #3 $181.66   7.429%   $195.1555   $195.16   $195.15   $195.20  
  Purchase #4 $172.31   9.574%   $188.807   $188.81   $188.80   $188.80  
  Purchase #5 $158.43   4.284%   $165.2171   $165.22   $165.20   $165.20  
  Purchase #6 $203.93   3.165%   $210.3844   $210.38   $210.40   $210.40  
  Purchase #7 $248.53   6.284%   $264.1476   $264.15   $264.15   $264.10  
  7 purchase totals = $1,262.64       $1,355.7740   $1,355.79   $1,355.80   $1,355.80