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	$165.72	4.794%	$173.6646	$173.66	$173.65	$173.70
Purchase #2	$105.49	5.711%	$111.5145	$111.51	$111.50	$111.50
Purchase #3	$92.33	13.155%	$104.476	$104.48	$104.50	$104.50
Purchase #4	$211.79	7.718%	$228.136	$228.14	$228.15	$228.10
Purchase #5	$116.76	9.527%	$127.8837	$127.88	$127.90	$127.90
Purchase #6	$5.39	10.268%	$5.9434	$5.94	$5.95	$5.90
Purchase #7	$114.56	6.835%	$122.3902	$122.39	$122.40	$122.40
7 purchase totals =	$812.04		$874.0084	$874.00	$874.05	$874.00