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 $65.65   6.718%   $70.0604   $70.06   $70.05   $70.10  
  Purchase #2 $217.91   8.726%   $236.9248   $236.92   $236.90   $236.90  
  Purchase #3 $52.58   8.749%   $57.1802   $57.18   $57.20   $57.20  
  Purchase #4 $58.29   11.404%   $64.9374   $64.94   $64.95   $64.90  
  Purchase #5 $239.85   9.812%   $263.3841   $263.38   $263.40   $263.40  
  Purchase #6 $231.81   8.111%   $250.6121   $250.61   $250.60   $250.60  
  Purchase #7 $182.68   12.142%   $204.861   $204.86   $204.85   $204.90  
  7 purchase totals = $1,048.77       $1,147.9600   $1,147.95   $1,147.95   $1,148.00