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 $201.82   7.159%   $216.2683   $216.27   $216.25   $216.30  
  Purchase #2 $85.91   9.558%   $94.1213   $94.12   $94.10   $94.10  
  Purchase #3 $233.28   3.428%   $241.2768   $241.28   $241.30   $241.30  
  Purchase #4 $63.97   9.279%   $69.9058   $69.91   $69.90   $69.90  
  Purchase #5 $83.57   12.758%   $94.2319   $94.23   $94.25   $94.20  
  Purchase #6 $71.42   3.659%   $74.0333   $74.03   $74.05   $74.00  
  Purchase #7 $101.34   4.230%   $105.6267   $105.63   $105.65   $105.60  
  7 purchase totals = $841.31       $895.4641   $895.47   $895.50   $895.40