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	$67.51	8.381%	$73.168	$73.17	$73.15	$73.20
Purchase #2	$159.60	4.631%	$166.9911	$166.99	$167.00	$167.00
Purchase #3	$178.60	6.639%	$190.4573	$190.46	$190.45	$190.50
Purchase #4	$194.63	5.667%	$205.6597	$205.66	$205.65	$205.70
Purchase #5	$120.27	9.670%	$131.9001	$131.90	$131.90	$131.90
Purchase #6	$175.89	13.397%	$199.454	$199.45	$199.45	$199.50
Purchase #7	$123.66	4.874%	$129.6872	$129.69	$129.70	$129.70
7 purchase totals =	$1,020.16		$1,097.3174	$1,097.32	$1,097.30	$1,097.50