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 $169.63   7.458%   $182.281   $182.28   $182.30   $182.30  
  Purchase #2 $222.63   8.632%   $241.8474   $241.85   $241.85   $241.80  
  Purchase #3 $53.65   5.138%   $56.4065   $56.41   $56.40   $56.40  
  Purchase #4 $211.34   5.802%   $223.6019   $223.60   $223.60   $223.60  
  Purchase #5 $163.72   7.657%   $176.256   $176.26   $176.25   $176.30  
  Purchase #6 $190.95   10.358%   $210.7286   $210.73   $210.75   $210.70  
  Purchase #7 $206.83   9.267%   $225.9969   $226.00   $226.00   $226.00  
  7 purchase totals = $1,218.75       $1,317.1183   $1,317.13   $1,317.15   $1,317.10