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	$159.78	5.264%	$168.1908	$168.19	$168.20	$168.20
Purchase #2	$11.66	8.117%	$12.6064	$12.61	$12.60	$12.60
Purchase #3	$67.36	5.717%	$71.211	$71.21	$71.20	$71.20
Purchase #4	$61.29	13.628%	$69.6426	$69.64	$69.65	$69.60
Purchase #5	$55.39	8.684%	$60.2001	$60.20	$60.20	$60.20
Purchase #6	$71.56	9.387%	$78.2773	$78.28	$78.30	$78.30
Purchase #7	$158.78	11.156%	$176.4935	$176.49	$176.50	$176.50
7 purchase totals =	$585.82		$636.6217	$636.62	$636.65	$636.60