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 $38.63   12.674%   $43.526   $43.53   $43.55   $43.50  
  Purchase #2 $196.77   8.315%   $213.1314   $213.13   $213.15   $213.10  
  Purchase #3 $39.38   6.414%   $41.9058   $41.91   $41.90   $41.90  
  Purchase #4 $243.93   5.258%   $256.7558   $256.76   $256.75   $256.80  
  Purchase #5 $133.51   4.619%   $139.6768   $139.68   $139.70   $139.70  
  Purchase #6 $191.58   7.678%   $206.2895   $206.29   $206.30   $206.30  
  Purchase #7 $50.52   3.735%   $52.4069   $52.41   $52.40   $52.40  
  7 purchase totals = $894.32       $953.6922   $953.71   $953.75   $953.70