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 $36.39   4.276%   $37.946   $37.95   $37.95   $37.90  
  Purchase #2 $53.85   10.213%   $59.3497   $59.35   $59.35   $59.30  
  Purchase #3 $41.78   11.573%   $46.6152   $46.62   $46.60   $46.60  
  Purchase #4 $209.67   3.581%   $217.1783   $217.18   $217.20   $217.20  
  Purchase #5 $14.65   8.279%   $15.8629   $15.86   $15.85   $15.90  
  Purchase #6 $175.51   11.652%   $195.9604   $195.96   $195.95   $196.00  
  Purchase #7 $243.87   6.353%   $259.3631   $259.36   $259.35   $259.40  
  7 purchase totals = $775.72       $832.2756   $832.28   $832.25   $832.30