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 $56.52   10.290%   $62.3359   $62.34   $62.35   $62.30  
  Purchase #2 $32.51   10.728%   $35.9977   $36.00   $36.00   $36.00  
  Purchase #3 $42.70   3.609%   $44.241   $44.24   $44.25   $44.20  
  Purchase #4 $245.72   7.841%   $264.9869   $264.99   $265.00   $265.00  
  Purchase #5 $171.59   8.785%   $186.6642   $186.66   $186.65   $186.70  
  Purchase #6 $65.43   10.132%   $72.0594   $72.06   $72.05   $72.10  
  Purchase #7 $244.46   13.601%   $277.709   $277.71   $277.70   $277.70  
  7 purchase totals = $858.93       $943.9941   $944.00   $944.00   $944.00