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 $118.92   5.606%   $125.5867   $125.59   $125.60   $125.60  
  Purchase #2 $150.59   11.149%   $167.3793   $167.38   $167.40   $167.40  
  Purchase #3 $169.99   11.591%   $189.6935   $189.69   $189.70   $189.70  
  Purchase #4 $239.47   3.661%   $248.237   $248.24   $248.25   $248.20  
  Purchase #5 $226.76   10.247%   $249.9961   $250.00   $250.00   $250.00  
  Purchase #6 $250.78   7.593%   $269.8217   $269.82   $269.80   $269.80  
  Purchase #7 $165.59   12.194%   $185.782   $185.78   $185.80   $185.80  
  7 purchase totals = $1,322.10       $1,436.4963   $1,436.50   $1,436.55   $1,436.50