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	$37.89	8.762%	$41.2099	$41.21	$41.20	$41.20
Purchase #2	$151.81	4.135%	$158.0873	$158.09	$158.10	$158.10
Purchase #3	$109.82	4.379%	$114.629	$114.63	$114.65	$114.60
Purchase #4	$235.82	3.358%	$243.7388	$243.74	$243.75	$243.70
Purchase #5	$172.79	10.263%	$190.5234	$190.52	$190.50	$190.50
Purchase #6	$226.47	10.605%	$250.4871	$250.49	$250.50	$250.50
Purchase #7	$70.60	11.569%	$78.7677	$78.77	$78.75	$78.80
7 purchase totals =	$1,005.20		$1,077.4432	$1,077.45	$1,077.45	$1,077.40