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 $57.47   11.445%   $64.0474   $64.05   $64.05   $64.00  
  Purchase #2 $96.71   8.286%   $104.7234   $104.72   $104.70   $104.70  
  Purchase #3 $214.44   5.531%   $226.3007   $226.30   $226.30   $226.30  
  Purchase #4 $215.58   4.738%   $225.7942   $225.79   $225.80   $225.80  
  Purchase #5 $247.52   8.185%   $267.7795   $267.78   $267.80   $267.80  
  Purchase #6 $28.94   10.555%   $31.9946   $31.99   $32.00   $32.00  
  Purchase #7 $95.73   8.113%   $103.4966   $103.50   $103.50   $103.50  
  7 purchase totals = $956.39       $1,024.1364   $1,024.13   $1,024.15   $1,024.10