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 $62.25   9.162%   $67.9533   $67.95   $67.95   $68.00  
  Purchase #2 $96.93   8.269%   $104.9451   $104.95   $104.95   $104.90  
  Purchase #3 $246.94   3.564%   $255.7409   $255.74   $255.75   $255.70  
  Purchase #4 $169.45   3.819%   $175.9213   $175.92   $175.90   $175.90  
  Purchase #5 $21.32   13.690%   $24.2387   $24.24   $24.25   $24.20  
  Purchase #6 $108.93   11.855%   $121.8437   $121.84   $121.85   $121.80  
  Purchase #7 $160.62   6.827%   $171.5855   $171.59   $171.60   $171.60  
  7 purchase totals = $866.44       $922.2285   $922.23   $922.25   $922.10