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 $224.68   4.457%   $234.694   $234.69   $234.70   $234.70  
  Purchase #2 $132.91   8.594%   $144.3323   $144.33   $144.35   $144.30  
  Purchase #3 $76.79   8.520%   $83.3325   $83.33   $83.35   $83.30  
  Purchase #4 $156.93   12.725%   $176.8993   $176.90   $176.90   $176.90  
  Purchase #5 $82.93   6.861%   $88.6198   $88.62   $88.60   $88.60  
  Purchase #6 $194.26   6.777%   $207.425   $207.43   $207.45   $207.40  
  Purchase #7 $192.66   11.534%   $214.8814   $214.88   $214.90   $214.90  
  7 purchase totals = $1,061.16       $1,150.1843   $1,150.18   $1,150.25   $1,150.10