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	$243.83	12.406%	$274.0795	$274.08	$274.10	$274.10
Purchase #2	$209.92	5.503%	$221.4719	$221.47	$221.45	$221.50
Purchase #3	$148.66	11.149%	$165.2341	$165.23	$165.25	$165.20
Purchase #4	$107.62	6.470%	$114.583	$114.58	$114.60	$114.60
Purchase #5	$78.78	3.859%	$81.8201	$81.82	$81.80	$81.80
Purchase #6	$196.91	4.473%	$205.7178	$205.72	$205.70	$205.70
Purchase #7	$107.70	3.744%	$111.7323	$111.73	$111.75	$111.70
7 purchase totals =	$1,093.42		$1,174.6387	$1,174.63	$1,174.65	$1,174.60