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 $93.72   4.104%   $97.5663   $97.57   $97.55   $97.60  
  Purchase #2 $194.80   10.865%   $215.965   $215.97   $215.95   $216.00  
  Purchase #3 $65.28   11.246%   $72.6214   $72.62   $72.60   $72.60  
  Purchase #4 $227.37   9.206%   $248.3017   $248.30   $248.30   $248.30  
  Purchase #5 $202.48   10.243%   $223.22   $223.22   $223.20   $223.20  
  Purchase #6 $112.75   10.543%   $124.6372   $124.64   $124.65   $124.60  
  Purchase #7 $117.63   3.592%   $121.8553   $121.86   $121.85   $121.90  
  7 purchase totals = $1,014.03       $1,104.1669   $1,104.18   $1,104.10   $1,104.20