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 $43.76   11.815%   $48.9302   $48.93   $48.95   $48.90  
  Purchase #2 $204.41   3.689%   $211.9507   $211.95   $211.95   $212.00  
  Purchase #3 $18.99   10.744%   $21.0303   $21.03   $21.05   $21.00  
  Purchase #4 $168.58   7.106%   $180.5593   $180.56   $180.55   $180.60  
  Purchase #5 $158.84   8.472%   $172.2969   $172.30   $172.30   $172.30  
  Purchase #6 $148.94   8.517%   $161.6252   $161.63   $161.65   $161.60  
  Purchase #7 $25.44   6.580%   $27.114   $27.11   $27.10   $27.10  
  7 purchase totals = $768.96       $823.5066   $823.51   $823.55   $823.50