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	$155.33	6.631%	$165.6299	$165.63	$165.65	$165.60
Purchase #2	$242.67	13.511%	$275.4571	$275.46	$275.45	$275.50
Purchase #3	$108.44	5.375%	$114.2687	$114.27	$114.25	$114.30
Purchase #4	$160.36	11.752%	$179.2055	$179.21	$179.20	$179.20
Purchase #5	$135.86	13.635%	$154.3845	$154.38	$154.40	$154.40
Purchase #6	$117.75	11.852%	$131.7057	$131.71	$131.70	$131.70
Purchase #7	$50.30	6.661%	$53.6505	$53.65	$53.65	$53.70
7 purchase totals =	$970.71		$1,074.3019	$1,074.31	$1,074.30	$1,074.40