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 $208.83   11.719%   $233.3028   $233.30   $233.30   $233.30  
  Purchase #2 $206.94   9.572%   $226.7483   $226.75   $226.75   $226.70  
  Purchase #3 $75.95   12.781%   $85.6572   $85.66   $85.65   $85.70  
  Purchase #4 $101.69   13.755%   $115.6775   $115.68   $115.70   $115.70  
  Purchase #5 $223.78   10.423%   $247.1046   $247.10   $247.10   $247.10  
  Purchase #6 $63.73   5.380%   $67.1587   $67.16   $67.15   $67.20  
  Purchase #7 $180.49   9.760%   $198.1058   $198.11   $198.10   $198.10  
  7 purchase totals = $1,061.41       $1,173.7549   $1,173.76   $1,173.75   $1,173.80