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 $84.60   12.826%   $95.4508   $95.45   $95.45   $95.50  
  Purchase #2 $145.74   11.794%   $162.9286   $162.93   $162.95   $162.90  
  Purchase #3 $167.58   3.762%   $173.8844   $173.88   $173.90   $173.90  
  Purchase #4 $88.93   5.602%   $93.9119   $93.91   $93.90   $93.90  
  Purchase #5 $112.37   7.364%   $120.6449   $120.64   $120.65   $120.60  
  Purchase #6 $80.63   3.146%   $83.1666   $83.17   $83.15   $83.20  
  Purchase #7 $69.86   10.120%   $76.9298   $76.93   $76.95   $76.90  
  7 purchase totals = $749.71       $806.9170   $806.91   $806.95   $806.90