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	$102.73	11.873%	$114.9271	$114.93	$114.95	$114.90
Purchase #2	$170.81	3.422%	$176.6551	$176.66	$176.65	$176.70
Purchase #3	$92.35	8.574%	$100.2681	$100.27	$100.25	$100.30
Purchase #4	$129.94	11.451%	$144.8194	$144.82	$144.80	$144.80
Purchase #5	$171.40	6.610%	$182.7295	$182.73	$182.75	$182.70
Purchase #6	$175.28	12.320%	$196.8745	$196.87	$196.85	$196.90
Purchase #7	$218.93	13.851%	$249.254	$249.25	$249.25	$249.30
7 purchase totals =	$1,061.44		$1,165.5277	$1,165.53	$1,165.50	$1,165.60