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	$199.95	12.223%	$224.3899	$224.39	$224.40	$224.40
Purchase #2	$230.42	12.538%	$259.3101	$259.31	$259.30	$259.30
Purchase #3	$147.27	4.620%	$154.0739	$154.07	$154.05	$154.10
Purchase #4	$172.89	13.635%	$196.4636	$196.46	$196.45	$196.50
Purchase #5	$103.74	5.485%	$109.4301	$109.43	$109.45	$109.40
Purchase #6	$43.83	4.397%	$45.7572	$45.76	$45.75	$45.80
Purchase #7	$184.65	3.618%	$191.3306	$191.33	$191.35	$191.30
7 purchase totals =	$1,082.75		$1,180.7554	$1,180.75	$1,180.75	$1,180.80