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 $182.78   7.251%   $196.0334   $196.03   $196.05   $196.00  
  Purchase #2 $129.96   10.240%   $143.2679   $143.27   $143.25   $143.30  
  Purchase #3 $104.46   5.650%   $110.362   $110.36   $110.35   $110.40  
  Purchase #4 $213.43   10.104%   $234.995   $235.00   $235.00   $235.00  
  Purchase #5 $60.34   4.258%   $62.9093   $62.91   $62.90   $62.90  
  Purchase #6 $55.92   11.232%   $62.2009   $62.20   $62.20   $62.20  
  Purchase #7 $62.58   3.542%   $64.7966   $64.80   $64.80   $64.80  
  7 purchase totals = $809.47       $874.5651   $874.57   $874.55   $874.60