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 $97.27   11.287%   $108.2489   $108.25   $108.25   $108.20  
  Purchase #2 $204.41   9.380%   $223.5837   $223.58   $223.60   $223.60  
  Purchase #3 $203.38   7.753%   $219.1481   $219.15   $219.15   $219.10  
  Purchase #4 $70.86   5.278%   $74.6   $74.60   $74.60   $74.60  
  Purchase #5 $6.48   3.859%   $6.7301   $6.73   $6.75   $6.70  
  Purchase #6 $28.94   13.664%   $32.8944   $32.89   $32.90   $32.90  
  Purchase #7 $94.47   4.431%   $98.656   $98.66   $98.65   $98.70  
  7 purchase totals = $705.81       $763.8612   $763.86   $763.90   $763.80