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 $58.72   9.450%   $64.269   $64.27   $64.25   $64.30  
  Purchase #2 $48.40   9.719%   $53.104   $53.10   $53.10   $53.10  
  Purchase #3 $122.30   3.448%   $126.5169   $126.52   $126.50   $126.50  
  Purchase #4 $184.70   11.842%   $206.5722   $206.57   $206.55   $206.60  
  Purchase #5 $41.33   6.368%   $43.9619   $43.96   $43.95   $44.00  
  Purchase #6 $139.81   13.777%   $159.0716   $159.07   $159.05   $159.10  
  Purchase #7 $93.48   10.564%   $103.3552   $103.36   $103.35   $103.40  
  7 purchase totals = $688.74       $756.8508   $756.85   $756.75   $757.00