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 $119.76   4.154%   $124.7348   $124.73   $124.75   $124.70  
  Purchase #2 $110.82   6.632%   $118.1696   $118.17   $118.15   $118.20  
  Purchase #3 $160.59   10.468%   $177.4006   $177.40   $177.40   $177.40  
  Purchase #4 $195.58   3.625%   $202.6698   $202.67   $202.65   $202.70  
  Purchase #5 $217.59   8.610%   $236.3245   $236.32   $236.30   $236.30  
  Purchase #6 $228.62   9.825%   $251.0819   $251.08   $251.10   $251.10  
  Purchase #7 $219.64   10.789%   $243.337   $243.34   $243.35   $243.30  
  7 purchase totals = $1,252.60       $1,353.7182   $1,353.71   $1,353.70   $1,353.70