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 $118.64   7.583%   $127.6365   $127.64   $127.65   $127.60  
  Purchase #2 $66.28   4.638%   $69.3541   $69.35   $69.35   $69.40  
  Purchase #3 $146.34   12.613%   $164.7979   $164.80   $164.80   $164.80  
  Purchase #4 $184.63   8.479%   $200.2848   $200.28   $200.30   $200.30  
  Purchase #5 $55.29   10.311%   $60.991   $60.99   $61.00   $61.00  
  Purchase #6 $8.66   5.246%   $9.1143   $9.11   $9.10   $9.10  
  Purchase #7 $121.54   8.116%   $131.4042   $131.40   $131.40   $131.40  
  7 purchase totals = $701.38       $763.5828   $763.57   $763.60   $763.60