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	$173.95	13.147%	$196.8192	$196.82	$196.80	$196.80
Purchase #2	$243.52	9.500%	$266.6544	$266.65	$266.65	$266.70
Purchase #3	$13.65	13.609%	$15.5076	$15.51	$15.50	$15.50
Purchase #4	$9.29	6.222%	$9.868	$9.87	$9.85	$9.90
Purchase #5	$217.32	4.471%	$227.0364	$227.04	$227.05	$227.00
Purchase #6	$80.46	11.560%	$89.7612	$89.76	$89.75	$89.80
Purchase #7	$225.73	5.507%	$238.161	$238.16	$238.15	$238.20
7 purchase totals =	$963.92		$1,043.8078	$1,043.81	$1,043.75	$1,043.90