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 $95.46   9.777%   $104.7931   $104.79   $104.80   $104.80  
  Purchase #2 $174.56   6.138%   $185.2745   $185.27   $185.25   $185.30  
  Purchase #3 $24.81   8.434%   $26.9025   $26.90   $26.90   $26.90  
  Purchase #4 $45.79   10.382%   $50.5439   $50.54   $50.55   $50.50  
  Purchase #5 $119.80   5.344%   $126.2021   $126.20   $126.20   $126.20  
  Purchase #6 $159.52   4.308%   $166.3921   $166.39   $166.40   $166.40  
  Purchase #7 $193.93   5.847%   $205.2691   $205.27   $205.25   $205.30  
  7 purchase totals = $813.87       $865.3773   $865.36   $865.35   $865.40