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 $58.57   5.752%   $61.9389   $61.94   $61.95   $61.90  
  Purchase #2 $186.79   5.160%   $196.4284   $196.43   $196.45   $196.40  
  Purchase #3 $196.61   11.750%   $219.7117   $219.71   $219.70   $219.70  
  Purchase #4 $218.78   9.786%   $240.1898   $240.19   $240.20   $240.20  
  Purchase #5 $93.92   3.738%   $97.4307   $97.43   $97.45   $97.40  
  Purchase #6 $13.76   7.327%   $14.7682   $14.77   $14.75   $14.80  
  Purchase #7 $64.75   9.425%   $70.8527   $70.85   $70.85   $70.90  
  7 purchase totals = $833.18       $901.3204   $901.32   $901.35   $901.30