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 $68.78   4.633%   $71.9666   $71.97   $71.95   $72.00  
  Purchase #2 $190.48   12.631%   $214.5395   $214.54   $214.55   $214.50  
  Purchase #3 $237.74   10.430%   $262.5363   $262.54   $262.55   $262.50  
  Purchase #4 $27.35   3.758%   $28.3778   $28.38   $28.40   $28.40  
  Purchase #5 $248.46   8.312%   $269.112   $269.11   $269.10   $269.10  
  Purchase #6 $139.94   11.462%   $155.9799   $155.98   $156.00   $156.00  
  Purchase #7 $54.52   10.250%   $60.1083   $60.11   $60.10   $60.10  
  7 purchase totals = $967.27       $1,062.6204   $1,062.63   $1,062.65   $1,062.60