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 $62.51   8.249%   $67.6664   $67.67   $67.65   $67.70  
  Purchase #2 $115.38   4.563%   $120.6448   $120.64   $120.65   $120.60  
  Purchase #3 $219.98   10.134%   $242.2728   $242.27   $242.25   $242.30  
  Purchase #4 $162.94   6.325%   $173.246   $173.25   $173.25   $173.20  
  Purchase #5 $196.28   9.418%   $214.7657   $214.77   $214.75   $214.80  
  Purchase #6 $197.46   4.204%   $205.7612   $205.76   $205.75   $205.80  
  Purchase #7 $152.46   7.571%   $164.0027   $164.00   $164.00   $164.00  
  7 purchase totals = $1,107.01       $1,188.3596   $1,188.36   $1,188.30   $1,188.40