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 $84.79   13.163%   $95.9509   $95.95   $95.95   $96.00  
  Purchase #2 $210.84   7.147%   $225.9087   $225.91   $225.90   $225.90  
  Purchase #3 $21.48   4.620%   $22.4724   $22.47   $22.45   $22.50  
  Purchase #4 $182.44   9.334%   $199.4689   $199.47   $199.45   $199.50  
  Purchase #5 $14.27   11.257%   $15.8764   $15.88   $15.90   $15.90  
  Purchase #6 $231.97   3.619%   $240.365   $240.37   $240.35   $240.40  
  Purchase #7 $6.33   8.734%   $6.8829   $6.88   $6.90   $6.90  
  7 purchase totals = $752.12       $806.9252   $806.93   $806.90   $807.10