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 $182.95   12.158%   $205.1931   $205.19   $205.20   $205.20  
  Purchase #2 $88.49   3.680%   $91.7464   $91.75   $91.75   $91.70  
  Purchase #3 $239.95   4.857%   $251.6044   $251.60   $251.60   $251.60  
  Purchase #4 $109.80   4.140%   $114.3457   $114.35   $114.35   $114.30  
  Purchase #5 $233.43   12.607%   $262.8585   $262.86   $262.85   $262.90  
  Purchase #6 $90.60   7.143%   $97.0716   $97.07   $97.05   $97.10  
  Purchase #7 $67.72   5.426%   $71.3945   $71.39   $71.40   $71.40  
  7 purchase totals = $1,012.94       $1,094.2142   $1,094.21   $1,094.20   $1,094.20