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 $42.62   5.487%   $44.9586   $44.96   $44.95   $45.00  
  Purchase #2 $229.87   6.526%   $244.8713   $244.87   $244.85   $244.90  
  Purchase #3 $101.47   10.189%   $111.8088   $111.81   $111.80   $111.80  
  Purchase #4 $235.92   4.486%   $246.5034   $246.50   $246.50   $246.50  
  Purchase #5 $235.47   13.516%   $267.2961   $267.30   $267.30   $267.30  
  Purchase #6 $38.61   8.771%   $41.9965   $42.00   $42.00   $42.00  
  Purchase #7 $146.38   9.788%   $160.7077   $160.71   $160.70   $160.70  
  7 purchase totals = $1,030.34       $1,118.1424   $1,118.15   $1,118.10   $1,118.20