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 $244.66   9.205%   $267.181   $267.18   $267.20   $267.20  
  Purchase #2 $94.87   8.713%   $103.136   $103.14   $103.15   $103.10  
  Purchase #3 $96.65   4.804%   $101.2931   $101.29   $101.30   $101.30  
  Purchase #4 $162.59   13.368%   $184.325   $184.33   $184.35   $184.30  
  Purchase #5 $63.66   5.336%   $67.0569   $67.06   $67.05   $67.10  
  Purchase #6 $119.32   11.335%   $132.8449   $132.84   $132.85   $132.80  
  Purchase #7 $98.96   3.172%   $102.099   $102.10   $102.10   $102.10  
  7 purchase totals = $880.71       $957.9359   $957.94   $958.00   $957.90