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 $204.96   4.748%   $214.6915   $214.69   $214.70   $214.70  
  Purchase #2 $195.62   12.807%   $220.6731   $220.67   $220.65   $220.70  
  Purchase #3 $72.31   9.667%   $79.3002   $79.30   $79.30   $79.30  
  Purchase #4 $89.64   8.254%   $97.0389   $97.04   $97.05   $97.00  
  Purchase #5 $9.25   5.653%   $9.7729   $9.77   $9.75   $9.80  
  Purchase #6 $114.86   3.328%   $118.6825   $118.68   $118.70   $118.70  
  Purchase #7 $248.96   6.360%   $264.7939   $264.79   $264.80   $264.80  
  7 purchase totals = $935.60       $1,004.9530   $1,004.94   $1,004.95   $1,005.00