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 $146.68   11.121%   $162.9923   $162.99   $163.00   $163.00  
  Purchase #2 $183.53   8.213%   $198.6033   $198.60   $198.60   $198.60  
  Purchase #3 $82.95   3.857%   $86.1494   $86.15   $86.15   $86.10  
  Purchase #4 $194.90   9.436%   $213.2908   $213.29   $213.30   $213.30  
  Purchase #5 $84.71   11.188%   $94.1874   $94.19   $94.20   $94.20  
  Purchase #6 $126.62   13.753%   $144.034   $144.03   $144.05   $144.00  
  Purchase #7 $178.47   13.172%   $201.9781   $201.98   $202.00   $202.00  
  7 purchase totals = $997.86       $1,101.2353   $1,101.23   $1,101.30   $1,101.20