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 $60.98   13.580%   $69.2611   $69.26   $69.25   $69.30  
  Purchase #2 $89.49   11.352%   $99.6489   $99.65   $99.65   $99.60  
  Purchase #3 $233.80   4.365%   $244.0054   $244.01   $244.00   $244.00  
  Purchase #4 $98.66   5.445%   $104.032   $104.03   $104.05   $104.00  
  Purchase #5 $228.30   8.265%   $247.169   $247.17   $247.15   $247.20  
  Purchase #6 $131.44   8.615%   $142.7636   $142.76   $142.75   $142.80  
  Purchase #7 $200.33   13.612%   $227.5989   $227.60   $227.60   $227.60  
  7 purchase totals = $1,043.00       $1,134.4789   $1,134.48   $1,134.45   $1,134.50