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 $41.41   8.388%   $44.8835   $44.88   $44.90   $44.90  
  Purchase #2 $235.97   10.743%   $261.3203   $261.32   $261.30   $261.30  
  Purchase #3 $105.92   10.810%   $117.37   $117.37   $117.35   $117.40  
  Purchase #4 $219.91   8.855%   $239.383   $239.38   $239.40   $239.40  
  Purchase #5 $207.52   8.431%   $225.016   $225.02   $225.00   $225.00  
  Purchase #6 $188.98   8.476%   $204.9979   $205.00   $205.00   $205.00  
  Purchase #7 $61.67   8.105%   $66.6684   $66.67   $66.65   $66.70  
  7 purchase totals = $1,061.38       $1,159.6391   $1,159.64   $1,159.60   $1,159.70