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 $205.99   9.811%   $226.1997   $226.20   $226.20   $226.20  
  Purchase #2 $176.63   11.734%   $197.3558   $197.36   $197.35   $197.40  
  Purchase #3 $115.74   4.211%   $120.6138   $120.61   $120.60   $120.60  
  Purchase #4 $54.40   5.664%   $57.4812   $57.48   $57.50   $57.50  
  Purchase #5 $195.67   6.180%   $207.7624   $207.76   $207.75   $207.80  
  Purchase #6 $192.37   11.345%   $214.1944   $214.19   $214.20   $214.20  
  Purchase #7 $147.59   11.598%   $164.7075   $164.71   $164.70   $164.70  
  7 purchase totals = $1,088.39       $1,188.3148   $1,188.31   $1,188.30   $1,188.40