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 $87.75   7.174%   $94.0452   $94.05   $94.05   $94.00  
  Purchase #2 $145.49   12.218%   $163.266   $163.27   $163.25   $163.30  
  Purchase #3 $67.28   9.415%   $73.6144   $73.61   $73.60   $73.60  
  Purchase #4 $176.78   10.732%   $195.752   $195.75   $195.75   $195.80  
  Purchase #5 $131.86   4.231%   $137.439   $137.44   $137.45   $137.40  
  Purchase #6 $151.55   7.554%   $162.9981   $163.00   $163.00   $163.00  
  Purchase #7 $135.40   10.313%   $149.3638   $149.36   $149.35   $149.40  
  7 purchase totals = $896.11       $976.4785   $976.48   $976.45   $976.50