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 $186.41   4.624%   $195.0296   $195.03   $195.05   $195.00  
  Purchase #2 $45.60   4.682%   $47.735   $47.74   $47.75   $47.70  
  Purchase #3 $18.40   12.453%   $20.6914   $20.69   $20.70   $20.70  
  Purchase #4 $153.82   6.338%   $163.5691   $163.57   $163.55   $163.60  
  Purchase #5 $58.89   10.358%   $64.9898   $64.99   $65.00   $65.00  
  Purchase #6 $83.68   3.456%   $86.572   $86.57   $86.55   $86.60  
  Purchase #7 $162.51   11.118%   $180.5779   $180.58   $180.60   $180.60  
  7 purchase totals = $709.31       $759.1648   $759.17   $759.20   $759.20