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 $184.44   4.244%   $192.2676   $192.27   $192.25   $192.30  
  Purchase #2 $30.63   5.253%   $32.239   $32.24   $32.25   $32.20  
  Purchase #3 $84.82   12.427%   $95.3606   $95.36   $95.35   $95.40  
  Purchase #4 $208.70   7.379%   $224.1   $224.10   $224.10   $224.10  
  Purchase #5 $193.90   8.145%   $209.6932   $209.69   $209.70   $209.70  
  Purchase #6 $207.49   12.532%   $233.4926   $233.49   $233.50   $233.50  
  Purchase #7 $116.49   5.411%   $122.7933   $122.79   $122.80   $122.80  
  7 purchase totals = $1,026.47       $1,109.9463   $1,109.94   $1,109.95   $1,110.00