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 $164.26   9.440%   $179.7661   $179.77   $179.75   $179.80  
  Purchase #2 $176.96   4.389%   $184.7268   $184.73   $184.75   $184.70  
  Purchase #3 $232.27   8.238%   $251.4044   $251.40   $251.40   $251.40  
  Purchase #4 $160.74   7.238%   $172.3744   $172.37   $172.35   $172.40  
  Purchase #5 $183.78   6.222%   $195.2148   $195.21   $195.20   $195.20  
  Purchase #6 $177.37   10.846%   $196.6076   $196.61   $196.60   $196.60  
  Purchase #7 $146.63   11.366%   $163.296   $163.30   $163.30   $163.30  
  7 purchase totals = $1,242.01       $1,343.3901   $1,343.39   $1,343.35   $1,343.40