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 $91.95   3.602%   $95.262   $95.26   $95.25   $95.30  
  Purchase #2 $66.88   13.133%   $75.6634   $75.66   $75.65   $75.70  
  Purchase #3 $90.54   6.262%   $96.2096   $96.21   $96.20   $96.20  
  Purchase #4 $154.36   8.693%   $167.7785   $167.78   $167.80   $167.80  
  Purchase #5 $241.99   9.696%   $265.4534   $265.45   $265.45   $265.50  
  Purchase #6 $162.39   12.661%   $182.9502   $182.95   $182.95   $183.00  
  Purchase #7 $234.48   12.110%   $262.8755   $262.88   $262.90   $262.90  
  7 purchase totals = $1,042.59       $1,146.1926   $1,146.19   $1,146.20   $1,146.40