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 $75.43   8.853%   $82.1078   $82.11   $82.10   $82.10  
  Purchase #2 $161.87   3.391%   $167.359   $167.36   $167.35   $167.40  
  Purchase #3 $56.63   11.829%   $63.3288   $63.33   $63.35   $63.30  
  Purchase #4 $180.75   11.131%   $200.8693   $200.87   $200.85   $200.90  
  Purchase #5 $174.69   12.195%   $195.9934   $195.99   $196.00   $196.00  
  Purchase #6 $187.36   12.208%   $210.2329   $210.23   $210.25   $210.20  
  Purchase #7 $123.31   8.314%   $133.562   $133.56   $133.55   $133.60  
  7 purchase totals = $960.04       $1,053.4532   $1,053.45   $1,053.45   $1,053.50