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 $164.52   7.313%   $176.5513   $176.55   $176.55   $176.60  
  Purchase #2 $214.69   8.700%   $233.368   $233.37   $233.35   $233.40  
  Purchase #3 $56.44   5.789%   $59.7073   $59.71   $59.70   $59.70  
  Purchase #4 $226.42   5.681%   $239.2829   $239.28   $239.30   $239.30  
  Purchase #5 $199.50   10.361%   $220.1702   $220.17   $220.15   $220.20  
  Purchase #6 $169.39   12.767%   $191.016   $191.02   $191.00   $191.00  
  Purchase #7 $136.28   4.355%   $142.215   $142.22   $142.20   $142.20  
  7 purchase totals = $1,167.24       $1,262.3107   $1,262.32   $1,262.25   $1,262.40