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 $76.49   8.428%   $82.9366   $82.94   $82.95   $82.90  
  Purchase #2 $35.69   5.529%   $37.6633   $37.66   $37.65   $37.70  
  Purchase #3 $63.29   9.814%   $69.5013   $69.50   $69.50   $69.50  
  Purchase #4 $83.38   9.687%   $91.457   $91.46   $91.45   $91.50  
  Purchase #5 $113.40   3.781%   $117.6877   $117.69   $117.70   $117.70  
  Purchase #6 $152.91   11.632%   $170.6965   $170.70   $170.70   $170.70  
  Purchase #7 $201.45   5.366%   $212.2598   $212.26   $212.25   $212.30  
  7 purchase totals = $726.61       $782.2022   $782.21   $782.20   $782.30