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 $45.93   3.267%   $47.4305   $47.43   $47.45   $47.40  
  Purchase #2 $54.72   7.549%   $58.8508   $58.85   $58.85   $58.90  
  Purchase #3 $69.39   3.319%   $71.6931   $71.69   $71.70   $71.70  
  Purchase #4 $83.46   6.832%   $89.162   $89.16   $89.15   $89.20  
  Purchase #5 $212.62   10.652%   $235.2683   $235.27   $235.25   $235.30  
  Purchase #6 $186.84   4.412%   $195.0834   $195.08   $195.10   $195.10  
  Purchase #7 $96.33   8.370%   $104.3928   $104.39   $104.40   $104.40  
  7 purchase totals = $749.29       $801.8809   $801.87   $801.90   $802.00