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 $202.58   7.555%   $217.8849   $217.88   $217.90   $217.90  
  Purchase #2 $218.59   10.537%   $241.6228   $241.62   $241.60   $241.60  
  Purchase #3 $110.66   5.623%   $116.8824   $116.88   $116.90   $116.90  
  Purchase #4 $192.54   4.699%   $201.5875   $201.59   $201.60   $201.60  
  Purchase #5 $225.39   6.118%   $239.1794   $239.18   $239.20   $239.20  
  Purchase #6 $184.28   6.647%   $196.5291   $196.53   $196.55   $196.50  
  Purchase #7 $193.30   6.571%   $206.0017   $206.00   $206.00   $206.00  
  7 purchase totals = $1,327.34       $1,419.6878   $1,419.68   $1,419.75   $1,419.70