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 $68.56   3.294%   $70.8184   $70.82   $70.80   $70.80  
  Purchase #2 $131.94   8.638%   $143.337   $143.34   $143.35   $143.30  
  Purchase #3 $73.32   8.274%   $79.3865   $79.39   $79.40   $79.40  
  Purchase #4 $236.31   10.373%   $260.8224   $260.82   $260.80   $260.80  
  Purchase #5 $197.55   8.652%   $214.642   $214.64   $214.65   $214.60  
  Purchase #6 $215.93   9.734%   $236.9486   $236.95   $236.95   $236.90  
  Purchase #7 $95.48   3.613%   $98.9297   $98.93   $98.95   $98.90  
  7 purchase totals = $1,019.09       $1,104.8846   $1,104.89   $1,104.90   $1,104.70