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 $191.51   7.486%   $205.8464   $205.85   $205.85   $205.80  
  Purchase #2 $42.36   9.457%   $46.366   $46.37   $46.35   $46.40  
  Purchase #3 $63.94   7.277%   $68.5929   $68.59   $68.60   $68.60  
  Purchase #4 $97.92   6.618%   $104.4003   $104.40   $104.40   $104.40  
  Purchase #5 $186.79   4.232%   $194.695   $194.70   $194.70   $194.70  
  Purchase #6 $248.68   5.657%   $262.7478   $262.75   $262.75   $262.70  
  Purchase #7 $62.92   6.624%   $67.0878   $67.09   $67.10   $67.10  
  7 purchase totals = $894.12       $949.7362   $949.75   $949.75   $949.70