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 $212.38   11.575%   $236.963   $236.96   $236.95   $237.00  
  Purchase #2 $144.40   7.808%   $155.6748   $155.67   $155.65   $155.70  
  Purchase #3 $180.69   6.206%   $191.9036   $191.90   $191.90   $191.90  
  Purchase #4 $14.59   9.546%   $15.9828   $15.98   $16.00   $16.00  
  Purchase #5 $203.56   5.844%   $215.456   $215.46   $215.45   $215.50  
  Purchase #6 $164.34   4.713%   $172.0853   $172.09   $172.10   $172.10  
  Purchase #7 $188.85   9.153%   $206.1354   $206.14   $206.15   $206.10  
  7 purchase totals = $1,108.81       $1,194.2009   $1,194.20   $1,194.20   $1,194.30