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 $59.55   7.228%   $63.8543   $63.85   $63.85   $63.90  
  Purchase #2 $192.47   11.249%   $214.121   $214.12   $214.10   $214.10  
  Purchase #3 $234.41   9.410%   $256.468   $256.47   $256.45   $256.50  
  Purchase #4 $14.70   12.635%   $16.5573   $16.56   $16.55   $16.60  
  Purchase #5 $168.41   9.389%   $184.222   $184.22   $184.20   $184.20  
  Purchase #6 $170.78   12.649%   $192.382   $192.38   $192.40   $192.40  
  Purchase #7 $239.93   11.366%   $267.2004   $267.20   $267.20   $267.20  
  7 purchase totals = $1,080.25       $1,194.8050   $1,194.80   $1,194.75   $1,194.90