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 $47.58   10.575%   $52.6116   $52.61   $52.60   $52.60  
  Purchase #2 $233.44   10.180%   $257.2042   $257.20   $257.20   $257.20  
  Purchase #3 $178.29   12.509%   $200.5923   $200.59   $200.60   $200.60  
  Purchase #4 $193.48   4.773%   $202.7148   $202.71   $202.70   $202.70  
  Purchase #5 $46.48   6.689%   $49.589   $49.59   $49.60   $49.60  
  Purchase #6 $10.98   13.874%   $12.5034   $12.50   $12.50   $12.50  
  Purchase #7 $158.65   5.559%   $167.4694   $167.47   $167.45   $167.50  
  7 purchase totals = $868.90       $942.6847   $942.67   $942.65   $942.70