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 $50.35   6.285%   $53.5145   $53.51   $53.50   $53.50  
  Purchase #2 $96.62   5.819%   $102.2423   $102.24   $102.25   $102.20  
  Purchase #3 $69.51   10.520%   $76.8225   $76.82   $76.80   $76.80  
  Purchase #4 $141.73   6.554%   $151.019   $151.02   $151.00   $151.00  
  Purchase #5 $238.89   3.602%   $247.4948   $247.49   $247.50   $247.50  
  Purchase #6 $232.77   4.515%   $243.2796   $243.28   $243.30   $243.30  
  Purchase #7 $205.65   10.482%   $227.2062   $227.21   $227.20   $227.20  
  7 purchase totals = $1,035.52       $1,101.5789   $1,101.57   $1,101.55   $1,101.50