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 $174.83   12.854%   $197.3026   $197.30   $197.30   $197.30  
  Purchase #2 $149.60   11.334%   $166.5557   $166.56   $166.55   $166.60  
  Purchase #3 $229.76   10.199%   $253.1932   $253.19   $253.20   $253.20  
  Purchase #4 $44.82   4.154%   $46.6818   $46.68   $46.70   $46.70  
  Purchase #5 $206.39   8.855%   $224.6658   $224.67   $224.65   $224.70  
  Purchase #6 $233.43   6.228%   $247.968   $247.97   $247.95   $248.00  
  Purchase #7 $60.83   6.416%   $64.7329   $64.73   $64.75   $64.70  
  7 purchase totals = $1,099.66       $1,201.1000   $1,201.10   $1,201.10   $1,201.20