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 $92.52   3.435%   $95.6981   $95.70   $95.70   $95.70  
  Purchase #2 $188.92   7.564%   $203.2099   $203.21   $203.20   $203.20  
  Purchase #3 $132.47   10.626%   $146.5463   $146.55   $146.55   $146.50  
  Purchase #4 $202.78   7.113%   $217.2037   $217.20   $217.20   $217.20  
  Purchase #5 $249.49   3.207%   $257.4911   $257.49   $257.50   $257.50  
  Purchase #6 $231.73   5.462%   $244.3871   $244.39   $244.40   $244.40  
  Purchase #7 $22.68   13.598%   $25.764   $25.76   $25.75   $25.80  
  7 purchase totals = $1,120.59       $1,190.3002   $1,190.30   $1,190.30   $1,190.30