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 $86.98   7.678%   $93.6583   $93.66   $93.65   $93.70  
  Purchase #2 $238.49   8.349%   $258.4015   $258.40   $258.40   $258.40  
  Purchase #3 $212.69   4.697%   $222.68   $222.68   $222.70   $222.70  
  Purchase #4 $234.94   3.224%   $242.5145   $242.51   $242.50   $242.50  
  Purchase #5 $146.55   8.874%   $159.5548   $159.55   $159.55   $159.60  
  Purchase #6 $61.49   4.210%   $64.0787   $64.08   $64.10   $64.10  
  Purchase #7 $201.73   9.703%   $221.3039   $221.30   $221.30   $221.30  
  7 purchase totals = $1,182.87       $1,262.1917   $1,262.18   $1,262.20   $1,262.30