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 $106.82   6.648%   $113.9214   $113.92   $113.90   $113.90  
  Purchase #2 $212.77   8.853%   $231.6065   $231.61   $231.60   $231.60  
  Purchase #3 $160.35   9.562%   $175.6827   $175.68   $175.70   $175.70  
  Purchase #4 $101.26   5.102%   $106.4263   $106.43   $106.45   $106.40  
  Purchase #5 $183.98   3.150%   $189.7754   $189.78   $189.80   $189.80  
  Purchase #6 $175.25   11.105%   $194.7115   $194.71   $194.70   $194.70  
  Purchase #7 $181.95   7.424%   $195.458   $195.46   $195.45   $195.50  
  7 purchase totals = $1,122.38       $1,207.5818   $1,207.59   $1,207.60   $1,207.60