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 $55.59   12.769%   $62.6883   $62.69   $62.70   $62.70  
  Purchase #2 $159.97   8.561%   $173.665   $173.67   $173.65   $173.70  
  Purchase #3 $14.81   8.103%   $16.0101   $16.01   $16.00   $16.00  
  Purchase #4 $196.38   3.288%   $202.837   $202.84   $202.85   $202.80  
  Purchase #5 $178.77   10.281%   $197.1493   $197.15   $197.15   $197.10  
  Purchase #6 $146.34   10.681%   $161.9706   $161.97   $161.95   $162.00  
  Purchase #7 $215.78   13.184%   $244.2284   $244.23   $244.25   $244.20  
  7 purchase totals = $967.64       $1,058.5487   $1,058.56   $1,058.55   $1,058.50