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 $119.95   3.401%   $124.0295   $124.03   $124.05   $124.00  
  Purchase #2 $192.97   8.612%   $209.5886   $209.59   $209.60   $209.60  
  Purchase #3 $79.37   9.449%   $86.8697   $86.87   $86.85   $86.90  
  Purchase #4 $185.92   4.788%   $194.8218   $194.82   $194.80   $194.80  
  Purchase #5 $78.67   12.383%   $88.4117   $88.41   $88.40   $88.40  
  Purchase #6 $158.50   8.300%   $171.6555   $171.66   $171.65   $171.70  
  Purchase #7 $211.74   10.409%   $233.78   $233.78   $233.80   $233.80  
  7 purchase totals = $1,027.12       $1,109.1568   $1,109.16   $1,109.15   $1,109.20