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	$134.25	11.140%	$149.2055	$149.21	$149.20	$149.20
Purchase #2	$62.91	13.170%	$71.1952	$71.20	$71.20	$71.20
Purchase #3	$42.51	11.737%	$47.4994	$47.50	$47.50	$47.50
Purchase #4	$34.32	8.152%	$37.1178	$37.12	$37.10	$37.10
Purchase #5	$114.70	11.490%	$127.879	$127.88	$127.90	$127.90
Purchase #6	$63.96	9.670%	$70.1449	$70.14	$70.15	$70.10
Purchase #7	$117.49	8.436%	$127.4015	$127.40	$127.40	$127.40
7 purchase totals =	$570.14		$630.4433	$630.45	$630.45	$630.40