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 $92.88   3.352%   $95.9933   $95.99   $96.00   $96.00  
  Purchase #2 $187.73   12.833%   $211.8214   $211.82   $211.80   $211.80  
  Purchase #3 $213.63   6.262%   $227.0075   $227.01   $227.00   $227.00  
  Purchase #4 $5.28   12.618%   $5.9462   $5.95   $5.95   $5.90  
  Purchase #5 $108.91   11.779%   $121.7385   $121.74   $121.75   $121.70  
  Purchase #6 $59.68   7.673%   $64.2592   $64.26   $64.25   $64.30  
  Purchase #7 $141.35   10.472%   $156.1522   $156.15   $156.15   $156.20  
  7 purchase totals = $809.46       $882.9183   $882.92   $882.90   $882.90