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 $235.28   12.607%   $264.9417   $264.94   $264.95   $264.90  
  Purchase #2 $225.71   4.690%   $236.2958   $236.30   $236.30   $236.30  
  Purchase #3 $217.90   11.766%   $243.5381   $243.54   $243.55   $243.50  
  Purchase #4 $197.26   10.479%   $217.9309   $217.93   $217.95   $217.90  
  Purchase #5 $154.58   12.829%   $174.4111   $174.41   $174.40   $174.40  
  Purchase #6 $116.26   7.643%   $125.1458   $125.15   $125.15   $125.10  
  Purchase #7 $193.82   4.762%   $203.0497   $203.05   $203.05   $203.00  
  7 purchase totals = $1,340.81       $1,465.3131   $1,465.32   $1,465.35   $1,465.10