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	$63.38	11.764%	$70.836	$70.84	$70.85	$70.80
Purchase #2	$9.49	9.539%	$10.3953	$10.40	$10.40	$10.40
Purchase #3	$238.48	3.745%	$247.4111	$247.41	$247.40	$247.40
Purchase #4	$220.77	10.746%	$244.4939	$244.49	$244.50	$244.50
Purchase #5	$172.76	10.131%	$190.2623	$190.26	$190.25	$190.30
Purchase #6	$140.40	3.216%	$144.9153	$144.92	$144.90	$144.90
Purchase #7	$92.36	13.842%	$105.1445	$105.14	$105.15	$105.10
7 purchase totals =	$937.64		$1,013.4584	$1,013.46	$1,013.45	$1,013.40