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 $197.58   8.826%   $215.0184   $215.02   $215.00   $215.00  
  Purchase #2 $213.61   5.261%   $224.848   $224.85   $224.85   $224.80  
  Purchase #3 $217.91   9.407%   $238.4088   $238.41   $238.40   $238.40  
  Purchase #4 $34.69   3.757%   $35.9933   $35.99   $36.00   $36.00  
  Purchase #5 $192.59   4.319%   $200.908   $200.91   $200.90   $200.90  
  Purchase #6 $126.90   11.283%   $141.2181   $141.22   $141.20   $141.20  
  Purchase #7 $97.65   8.848%   $106.2901   $106.29   $106.30   $106.30  
  7 purchase totals = $1,080.93       $1,162.6847   $1,162.69   $1,162.65   $1,162.60