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 $83.27   11.374%   $92.7411   $92.74   $92.75   $92.70  
  Purchase #2 $64.35   13.834%   $73.2522   $73.25   $73.25   $73.30  
  Purchase #3 $33.68   3.718%   $34.9322   $34.93   $34.95   $34.90  
  Purchase #4 $207.91   11.228%   $231.2541   $231.25   $231.25   $231.30  
  Purchase #5 $151.83   6.191%   $161.2298   $161.23   $161.25   $161.20  
  Purchase #6 $116.63   9.228%   $127.3926   $127.39   $127.40   $127.40  
  Purchase #7 $215.61   7.640%   $232.0826   $232.08   $232.10   $232.10  
  7 purchase totals = $873.28       $952.8846   $952.87   $952.95   $952.90