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 $71.55   7.564%   $76.962   $76.96   $76.95   $77.00  
  Purchase #2 $76.61   11.836%   $85.6776   $85.68   $85.70   $85.70  
  Purchase #3 $128.73   6.783%   $137.4618   $137.46   $137.45   $137.50  
  Purchase #4 $159.83   13.483%   $181.3799   $181.38   $181.40   $181.40  
  Purchase #5 $70.57   12.117%   $79.121   $79.12   $79.10   $79.10  
  Purchase #6 $101.64   4.708%   $106.4252   $106.43   $106.45   $106.40  
  Purchase #7 $231.98   6.434%   $246.9056   $246.91   $246.90   $246.90  
  7 purchase totals = $840.91       $913.9331   $913.94   $913.95   $914.00