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 $152.98   5.867%   $161.9553   $161.96   $161.95   $162.00  
  Purchase #2 $202.60   4.708%   $212.1384   $212.14   $212.15   $212.10  
  Purchase #3 $23.93   8.611%   $25.9906   $25.99   $26.00   $26.00  
  Purchase #4 $250.34   3.176%   $258.2908   $258.29   $258.30   $258.30  
  Purchase #5 $140.48   13.483%   $159.4209   $159.42   $159.40   $159.40  
  Purchase #6 $208.48   13.375%   $236.3642   $236.36   $236.35   $236.40  
  Purchase #7 $176.42   12.232%   $197.9997   $198.00   $198.00   $198.00  
  7 purchase totals = $1,155.23       $1,252.1599   $1,252.16   $1,252.15   $1,252.20