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 $173.33   12.861%   $195.622   $195.62   $195.60   $195.60  
  Purchase #2 $233.47   3.406%   $241.422   $241.42   $241.40   $241.40  
  Purchase #3 $243.81   13.696%   $277.2022   $277.20   $277.20   $277.20  
  Purchase #4 $122.72   7.149%   $131.4933   $131.49   $131.50   $131.50  
  Purchase #5 $141.96   6.690%   $151.4571   $151.46   $151.45   $151.50  
  Purchase #6 $84.78   4.608%   $88.6867   $88.69   $88.70   $88.70  
  Purchase #7 $245.65   6.147%   $260.7501   $260.75   $260.75   $260.80  
  7 purchase totals = $1,245.72       $1,346.6334   $1,346.63   $1,346.60   $1,346.70