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 $14.25   3.504%   $14.7493   $14.75   $14.75   $14.70  
  Purchase #2 $197.59   9.544%   $216.448   $216.45   $216.45   $216.40  
  Purchase #3 $163.96   4.744%   $171.7383   $171.74   $171.75   $171.70  
  Purchase #4 $48.57   3.629%   $50.3326   $50.33   $50.35   $50.30  
  Purchase #5 $162.35   12.320%   $182.3515   $182.35   $182.35   $182.40  
  Purchase #6 $249.29   4.642%   $260.862   $260.86   $260.85   $260.90  
  Purchase #7 $57.82   11.786%   $64.6347   $64.63   $64.65   $64.60  
  7 purchase totals = $893.83       $961.1164   $961.11   $961.15   $961.00