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 $94.26   4.443%   $98.448   $98.45   $98.45   $98.40  
  Purchase #2 $83.77   12.629%   $94.3493   $94.35   $94.35   $94.30  
  Purchase #3 $88.52   4.760%   $92.7336   $92.73   $92.75   $92.70  
  Purchase #4 $117.51   7.512%   $126.3374   $126.34   $126.35   $126.30  
  Purchase #5 $239.79   8.679%   $260.6014   $260.60   $260.60   $260.60  
  Purchase #6 $219.42   13.837%   $249.7811   $249.78   $249.80   $249.80  
  Purchase #7 $240.74   4.433%   $251.412   $251.41   $251.40   $251.40  
  7 purchase totals = $1,084.01       $1,173.6628   $1,173.66   $1,173.70   $1,173.50