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 $114.95   10.795%   $127.3589   $127.36   $127.35   $127.40  
  Purchase #2 $173.96   5.674%   $183.8305   $183.83   $183.85   $183.80  
  Purchase #3 $153.26   10.267%   $168.9952   $169.00   $169.00   $169.00  
  Purchase #4 $130.75   4.621%   $136.792   $136.79   $136.80   $136.80  
  Purchase #5 $13.95   9.731%   $15.3075   $15.31   $15.30   $15.30  
  Purchase #6 $126.38   13.405%   $143.3212   $143.32   $143.30   $143.30  
  Purchase #7 $248.59   3.209%   $256.5673   $256.57   $256.55   $256.60  
  7 purchase totals = $961.84       $1,032.1726   $1,032.18   $1,032.15   $1,032.20