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 $116.28   8.404%   $126.0522   $126.05   $126.05   $126.10  
  Purchase #2 $201.62   8.295%   $218.3444   $218.34   $218.35   $218.30  
  Purchase #3 $70.41   6.387%   $74.9071   $74.91   $74.90   $74.90  
  Purchase #4 $142.70   12.218%   $160.1351   $160.14   $160.15   $160.10  
  Purchase #5 $94.64   3.801%   $98.2373   $98.24   $98.25   $98.20  
  Purchase #6 $24.76   11.610%   $27.6346   $27.63   $27.65   $27.60  
  Purchase #7 $63.28   7.532%   $68.0462   $68.05   $68.05   $68.00  
  7 purchase totals = $713.69       $773.3569   $773.36   $773.40   $773.20