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 $34.94   7.631%   $37.6063   $37.61   $37.60   $37.60  
  Purchase #2 $166.52   13.681%   $189.3016   $189.30   $189.30   $189.30  
  Purchase #3 $69.52   7.158%   $74.4962   $74.50   $74.50   $74.50  
  Purchase #4 $245.50   9.143%   $267.9461   $267.95   $267.95   $267.90  
  Purchase #5 $40.81   11.349%   $45.4415   $45.44   $45.45   $45.40  
  Purchase #6 $120.28   4.277%   $125.4244   $125.42   $125.40   $125.40  
  Purchase #7 $11.74   3.756%   $12.181   $12.18   $12.20   $12.20  
  7 purchase totals = $689.31       $752.3971   $752.40   $752.40   $752.30