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 $46.63   11.770%   $52.1184   $52.12   $52.10   $52.10  
  Purchase #2 $80.72   6.372%   $85.8635   $85.86   $85.85   $85.90  
  Purchase #3 $89.55   6.130%   $95.0394   $95.04   $95.05   $95.00  
  Purchase #4 $85.76   10.845%   $95.0607   $95.06   $95.05   $95.10  
  Purchase #5 $182.42   5.385%   $192.2433   $192.24   $192.25   $192.20  
  Purchase #6 $236.61   13.282%   $268.0365   $268.04   $268.05   $268.00  
  Purchase #7 $62.34   9.798%   $68.4481   $68.45   $68.45   $68.40  
  7 purchase totals = $784.03       $856.8099   $856.81   $856.80   $856.70