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 $85.41   12.212%   $95.8403   $95.84   $95.85   $95.80  
  Purchase #2 $148.45   3.471%   $153.6027   $153.60   $153.60   $153.60  
  Purchase #3 $71.45   6.111%   $75.8163   $75.82   $75.80   $75.80  
  Purchase #4 $142.95   8.172%   $154.6319   $154.63   $154.65   $154.60  
  Purchase #5 $213.80   12.813%   $241.1942   $241.19   $241.20   $241.20  
  Purchase #6 $47.35   8.639%   $51.4406   $51.44   $51.45   $51.40  
  Purchase #7 $232.51   13.380%   $263.6198   $263.62   $263.60   $263.60  
  7 purchase totals = $941.92       $1,036.1458   $1,036.14   $1,036.15   $1,036.00