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 $44.95   3.624%   $46.579   $46.58   $46.60   $46.60  
  Purchase #2 $201.63   10.629%   $223.0613   $223.06   $223.05   $223.10  
  Purchase #3 $45.43   11.703%   $50.7467   $50.75   $50.75   $50.70  
  Purchase #4 $112.98   9.636%   $123.8668   $123.87   $123.85   $123.90  
  Purchase #5 $85.54   7.794%   $92.207   $92.21   $92.20   $92.20  
  Purchase #6 $121.62   8.790%   $132.3104   $132.31   $132.30   $132.30  
  Purchase #7 $225.72   6.316%   $239.9765   $239.98   $240.00   $240.00  
  7 purchase totals = $837.87       $908.7477   $908.76   $908.75   $908.80