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 $222.38   13.774%   $253.0106   $253.01   $253.00   $253.00  
  Purchase #2 $167.51   5.127%   $176.0982   $176.10   $176.10   $176.10  
  Purchase #3 $95.59   7.471%   $102.7315   $102.73   $102.75   $102.70  
  Purchase #4 $222.39   8.529%   $241.3576   $241.36   $241.35   $241.40  
  Purchase #5 $116.28   13.761%   $132.2813   $132.28   $132.30   $132.30  
  Purchase #6 $206.73   7.335%   $221.8936   $221.89   $221.90   $221.90  
  Purchase #7 $76.49   13.783%   $87.0326   $87.03   $87.05   $87.00  
  7 purchase totals = $1,107.37       $1,214.4054   $1,214.40   $1,214.45   $1,214.40