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 $13.76   5.352%   $14.4964   $14.50   $14.50   $14.50  
  Purchase #2 $118.71   3.862%   $123.2946   $123.29   $123.30   $123.30  
  Purchase #3 $161.85   4.836%   $169.6771   $169.68   $169.70   $169.70  
  Purchase #4 $204.64   6.487%   $217.915   $217.92   $217.90   $217.90  
  Purchase #5 $171.64   6.727%   $183.1862   $183.19   $183.20   $183.20  
  Purchase #6 $161.31   8.271%   $174.652   $174.65   $174.65   $174.70  
  Purchase #7 $156.34   10.335%   $172.4977   $172.50   $172.50   $172.50  
  7 purchase totals = $988.25       $1,055.7190   $1,055.73   $1,055.75   $1,055.80