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 $194.84   3.264%   $201.1996   $201.20   $201.20   $201.20  
  Purchase #2 $68.87   3.252%   $71.1097   $71.11   $71.10   $71.10  
  Purchase #3 $250.94   12.598%   $282.5534   $282.55   $282.55   $282.60  
  Purchase #4 $51.81   11.295%   $57.6619   $57.66   $57.65   $57.70  
  Purchase #5 $107.88   5.277%   $113.5728   $113.57   $113.55   $113.60  
  Purchase #6 $110.37   10.853%   $122.3485   $122.35   $122.35   $122.30  
  Purchase #7 $235.52   13.772%   $267.9558   $267.96   $267.95   $268.00  
  7 purchase totals = $1,020.23       $1,116.4017   $1,116.40   $1,116.35   $1,116.50