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 $190.47   5.687%   $201.302   $201.30   $201.30   $201.30  
  Purchase #2 $66.37   10.253%   $73.1749   $73.17   $73.15   $73.20  
  Purchase #3 $71.91   5.672%   $75.9887   $75.99   $76.00   $76.00  
  Purchase #4 $173.97   5.239%   $183.0843   $183.08   $183.10   $183.10  
  Purchase #5 $237.30   12.620%   $267.2473   $267.25   $267.25   $267.20  
  Purchase #6 $206.87   11.608%   $230.8835   $230.88   $230.90   $230.90  
  Purchase #7 $190.98   12.571%   $214.9881   $214.99   $215.00   $215.00  
  7 purchase totals = $1,137.87       $1,246.6688   $1,246.66   $1,246.70   $1,246.70