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 $60.54   3.620%   $62.7315   $62.73   $62.75   $62.70  
  Purchase #2 $6.32   4.856%   $6.6269   $6.63   $6.65   $6.60  
  Purchase #3 $153.96   10.531%   $170.1735   $170.17   $170.15   $170.20  
  Purchase #4 $41.81   10.467%   $46.1863   $46.19   $46.20   $46.20  
  Purchase #5 $202.55   10.547%   $223.9129   $223.91   $223.90   $223.90  
  Purchase #6 $135.51   9.314%   $148.1314   $148.13   $148.15   $148.10  
  Purchase #7 $63.54   7.445%   $68.2706   $68.27   $68.25   $68.30  
  7 purchase totals = $664.23       $726.0331   $726.03   $726.05   $726.00