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 $196.49   10.797%   $217.705   $217.71   $217.70   $217.70  
  Purchase #2 $245.83   3.807%   $255.1887   $255.19   $255.20   $255.20  
  Purchase #3 $34.51   6.442%   $36.7331   $36.73   $36.75   $36.70  
  Purchase #4 $250.65   10.648%   $277.3392   $277.34   $277.35   $277.30  
  Purchase #5 $182.36   5.554%   $192.4883   $192.49   $192.50   $192.50  
  Purchase #6 $129.58   11.793%   $144.8614   $144.86   $144.85   $144.90  
  Purchase #7 $216.87   3.752%   $225.007   $225.01   $225.00   $225.00  
  7 purchase totals = $1,256.29       $1,349.3227   $1,349.33   $1,349.35   $1,349.30