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 $194.60   4.244%   $202.8588   $202.86   $202.85   $202.90  
  Purchase #2 $221.95   8.377%   $240.5428   $240.54   $240.55   $240.50  
  Purchase #3 $180.89   10.385%   $199.6754   $199.68   $199.70   $199.70  
  Purchase #4 $188.64   10.752%   $208.9226   $208.92   $208.90   $208.90  
  Purchase #5 $197.70   9.815%   $217.1043   $217.10   $217.10   $217.10  
  Purchase #6 $211.39   7.564%   $227.3795   $227.38   $227.40   $227.40  
  Purchase #7 $149.89   11.546%   $167.1963   $167.20   $167.20   $167.20  
  7 purchase totals = $1,345.06       $1,463.6797   $1,463.68   $1,463.70   $1,463.70