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 $101.90   11.835%   $113.9599   $113.96   $113.95   $114.00  
  Purchase #2 $54.69   7.393%   $58.7332   $58.73   $58.75   $58.70  
  Purchase #3 $183.92   5.787%   $194.5635   $194.56   $194.55   $194.60  
  Purchase #4 $209.73   5.607%   $221.4896   $221.49   $221.50   $221.50  
  Purchase #5 $205.47   5.541%   $216.8551   $216.86   $216.85   $216.90  
  Purchase #6 $88.68   3.659%   $91.9248   $91.92   $91.90   $91.90  
  Purchase #7 $6.82   8.507%   $7.4002   $7.40   $7.40   $7.40  
  7 purchase totals = $851.21       $904.9263   $904.92   $904.90   $905.00