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 $84.64   12.322%   $95.0693   $95.07   $95.05   $95.10  
  Purchase #2 $104.92   10.129%   $115.5473   $115.55   $115.55   $115.50  
  Purchase #3 $104.30   9.849%   $114.5725   $114.57   $114.55   $114.60  
  Purchase #4 $188.89   7.642%   $203.325   $203.33   $203.35   $203.30  
  Purchase #5 $106.26   9.184%   $116.0189   $116.02   $116.00   $116.00  
  Purchase #6 $65.77   7.804%   $70.9027   $70.90   $70.90   $70.90  
  Purchase #7 $159.27   6.847%   $170.1752   $170.18   $170.20   $170.20  
  7 purchase totals = $814.05       $885.6109   $885.62   $885.60   $885.60