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 $23.84   10.327%   $26.302   $26.30   $26.30   $26.30  
  Purchase #2 $67.76   5.782%   $71.6779   $71.68   $71.70   $71.70  
  Purchase #3 $238.84   13.764%   $271.7139   $271.71   $271.70   $271.70  
  Purchase #4 $217.58   9.619%   $238.509   $238.51   $238.50   $238.50  
  Purchase #5 $204.95   3.567%   $212.2606   $212.26   $212.25   $212.30  
  Purchase #6 $221.61   3.564%   $229.5082   $229.51   $229.50   $229.50  
  Purchase #7 $62.34   3.682%   $64.6354   $64.64   $64.65   $64.60  
  7 purchase totals = $1,036.92       $1,114.6070   $1,114.61   $1,114.60   $1,114.60