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 $211.36   10.618%   $233.8022   $233.80   $233.80   $233.80  
  Purchase #2 $183.62   12.532%   $206.6313   $206.63   $206.65   $206.60  
  Purchase #3 $52.97   5.519%   $55.8934   $55.89   $55.90   $55.90  
  Purchase #4 $217.48   4.390%   $227.0274   $227.03   $227.05   $227.00  
  Purchase #5 $168.94   5.753%   $178.6591   $178.66   $178.65   $178.70  
  Purchase #6 $85.32   9.264%   $93.224   $93.22   $93.20   $93.20  
  Purchase #7 $211.42   12.589%   $238.0357   $238.04   $238.05   $238.00  
  7 purchase totals = $1,131.11       $1,233.2731   $1,233.27   $1,233.30   $1,233.20