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 $56.88   6.529%   $60.5937   $60.59   $60.60   $60.60  
  Purchase #2 $168.64   6.519%   $179.6336   $179.63   $179.65   $179.60  
  Purchase #3 $61.58   4.430%   $64.308   $64.31   $64.30   $64.30  
  Purchase #4 $185.33   12.571%   $208.6278   $208.63   $208.65   $208.60  
  Purchase #5 $228.29   6.419%   $242.9439   $242.94   $242.95   $242.90  
  Purchase #6 $94.37   8.598%   $102.4839   $102.48   $102.50   $102.50  
  Purchase #7 $236.99   4.163%   $246.8559   $246.86   $246.85   $246.90  
  7 purchase totals = $1,032.08       $1,105.4468   $1,105.44   $1,105.50   $1,105.40