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	$235.75	4.873%	$247.2381	$247.24	$247.25	$247.20
Purchase #2	$244.36	3.370%	$252.5949	$252.59	$252.60	$252.60
Purchase #3	$236.65	7.276%	$253.8687	$253.87	$253.85	$253.90
Purchase #4	$10.44	3.103%	$10.764	$10.76	$10.75	$10.80
Purchase #5	$57.35	3.600%	$59.4146	$59.41	$59.40	$59.40
Purchase #6	$145.45	13.824%	$165.557	$165.56	$165.55	$165.60
Purchase #7	$64.78	11.731%	$72.3793	$72.38	$72.40	$72.40
7 purchase totals =	$994.78		$1,061.8166	$1,061.81	$1,061.80	$1,061.90