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	$147.64	4.422%	$154.1686	$154.17	$154.15	$154.20
Purchase #2	$161.75	6.456%	$172.1926	$172.19	$172.20	$172.20
Purchase #3	$29.28	8.519%	$31.7744	$31.77	$31.75	$31.80
Purchase #4	$73.57	4.375%	$76.7887	$76.79	$76.80	$76.80
Purchase #5	$62.81	13.450%	$71.2579	$71.26	$71.25	$71.30
Purchase #6	$70.82	9.512%	$77.5564	$77.56	$77.55	$77.60
Purchase #7	$145.78	4.116%	$151.7803	$151.78	$151.80	$151.80
7 purchase totals =	$691.65		$735.5189	$735.52	$735.50	$735.70