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 $93.65   4.690%   $98.0422   $98.04   $98.05   $98.00  
  Purchase #2 $64.88   5.686%   $68.5691   $68.57   $68.55   $68.60  
  Purchase #3 $212.90   6.422%   $226.5724   $226.57   $226.55   $226.60  
  Purchase #4 $132.45   9.200%   $144.6354   $144.64   $144.65   $144.60  
  Purchase #5 $231.63   5.350%   $244.0222   $244.02   $244.00   $244.00  
  Purchase #6 $247.63   3.182%   $255.5096   $255.51   $255.50   $255.50  
  Purchase #7 $51.82   13.673%   $58.9053   $58.91   $58.90   $58.90  
  7 purchase totals = $1,034.96       $1,096.2562   $1,096.26   $1,096.20   $1,096.20