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 $67.87   6.472%   $72.2625   $72.26   $72.25   $72.30  
  Purchase #2 $190.49   6.872%   $203.5805   $203.58   $203.60   $203.60  
  Purchase #3 $105.54   4.811%   $110.6175   $110.62   $110.60   $110.60  
  Purchase #4 $168.27   4.517%   $175.8708   $175.87   $175.85   $175.90  
  Purchase #5 $189.68   3.740%   $196.774   $196.77   $196.75   $196.80  
  Purchase #6 $173.97   9.712%   $190.866   $190.87   $190.85   $190.90  
  Purchase #7 $110.65   13.539%   $125.6309   $125.63   $125.65   $125.60  
  7 purchase totals = $1,006.47       $1,075.6022   $1,075.60   $1,075.55   $1,075.70