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 $195.81   7.234%   $209.9749   $209.97   $209.95   $210.00  
  Purchase #2 $65.89   9.116%   $71.8965   $71.90   $71.90   $71.90  
  Purchase #3 $36.52   6.823%   $39.0118   $39.01   $39.00   $39.00  
  Purchase #4 $249.90   9.622%   $273.9454   $273.95   $273.95   $273.90  
  Purchase #5 $220.28   8.223%   $238.3936   $238.39   $238.40   $238.40  
  Purchase #6 $240.45   10.652%   $266.0627   $266.06   $266.05   $266.10  
  Purchase #7 $149.88   8.258%   $162.2571   $162.26   $162.25   $162.30  
  7 purchase totals = $1,158.73       $1,261.5420   $1,261.54   $1,261.50   $1,261.60