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 $68.72   7.734%   $74.0348   $74.03   $74.05   $74.00  
  Purchase #2 $237.58   12.475%   $267.2181   $267.22   $267.20   $267.20  
  Purchase #3 $19.96   7.589%   $21.4748   $21.47   $21.45   $21.50  
  Purchase #4 $5.56   11.396%   $6.1936   $6.19   $6.20   $6.20  
  Purchase #5 $94.90   6.274%   $100.854   $100.85   $100.85   $100.90  
  Purchase #6 $228.99   11.319%   $254.9094   $254.91   $254.90   $254.90  
  Purchase #7 $209.73   13.234%   $237.4857   $237.49   $237.50   $237.50  
  7 purchase totals = $865.44       $962.1704   $962.16   $962.15   $962.20