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 $94.82   7.307%   $101.7485   $101.75   $101.75   $101.70  
  Purchase #2 $11.91   3.186%   $12.2895   $12.29   $12.30   $12.30  
  Purchase #3 $222.84   3.634%   $230.938   $230.94   $230.95   $230.90  
  Purchase #4 $69.31   6.343%   $73.7063   $73.71   $73.70   $73.70  
  Purchase #5 $212.88   5.193%   $223.9349   $223.93   $223.95   $223.90  
  Purchase #6 $170.94   6.585%   $182.1964   $182.20   $182.20   $182.20  
  Purchase #7 $56.54   5.857%   $59.8515   $59.85   $59.85   $59.90  
  7 purchase totals = $839.24       $884.6651   $884.67   $884.70   $884.60