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 $41.52   8.225%   $44.935   $44.94   $44.95   $44.90  
  Purchase #2 $210.78   3.503%   $218.1636   $218.16   $218.15   $218.20  
  Purchase #3 $163.96   3.763%   $170.1298   $170.13   $170.15   $170.10  
  Purchase #4 $59.31   9.195%   $64.7636   $64.76   $64.75   $64.80  
  Purchase #5 $55.50   5.412%   $58.5037   $58.50   $58.50   $58.50  
  Purchase #6 $230.79   12.596%   $259.8603   $259.86   $259.85   $259.90  
  Purchase #7 $222.25   6.874%   $237.5275   $237.53   $237.55   $237.50  
  7 purchase totals = $984.11       $1,053.8835   $1,053.88   $1,053.90   $1,053.90