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	$64.32	9.209%	$70.2432	$70.24	$70.25	$70.20
Purchase #2	$67.97	8.591%	$73.8093	$73.81	$73.80	$73.80
Purchase #3	$75.37	3.873%	$78.2891	$78.29	$78.30	$78.30
Purchase #4	$106.64	4.842%	$111.8035	$111.80	$111.80	$111.80
Purchase #5	$71.80	3.492%	$74.3073	$74.31	$74.30	$74.30
Purchase #6	$146.27	8.764%	$159.0891	$159.09	$159.10	$159.10
Purchase #7	$152.56	8.714%	$165.8541	$165.85	$165.85	$165.90
7 purchase totals =	$684.93		$733.3956	$733.39	$733.40	$733.40