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 $69.46   10.562%   $76.7964   $76.80   $76.80   $76.80  
  Purchase #2 $29.95   8.348%   $32.4502   $32.45   $32.45   $32.50  
  Purchase #3 $191.96   7.834%   $206.9981   $207.00   $207.00   $207.00  
  Purchase #4 $181.92   3.471%   $188.2344   $188.23   $188.25   $188.20  
  Purchase #5 $208.85   4.452%   $218.148   $218.15   $218.15   $218.10  
  Purchase #6 $125.60   13.785%   $142.914   $142.91   $142.90   $142.90  
  Purchase #7 $60.31   3.255%   $62.2731   $62.27   $62.25   $62.30  
  7 purchase totals = $868.05       $927.8142   $927.81   $927.80   $927.80