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 $206.99   11.679%   $231.1644   $231.16   $231.15   $231.20  
  Purchase #2 $95.35   9.182%   $104.105   $104.11   $104.10   $104.10  
  Purchase #3 $128.76   11.692%   $143.8146   $143.81   $143.80   $143.80  
  Purchase #4 $87.92   11.189%   $97.7574   $97.76   $97.75   $97.80  
  Purchase #5 $244.62   7.639%   $263.3065   $263.31   $263.30   $263.30  
  Purchase #6 $49.81   10.276%   $54.9285   $54.93   $54.95   $54.90  
  Purchase #7 $125.72   11.143%   $139.729   $139.73   $139.75   $139.70  
  7 purchase totals = $939.17       $1,034.8054   $1,034.81   $1,034.80   $1,034.80