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	$154.39	4.529%	$161.3823	$161.38	$161.40	$161.40
Purchase #2	$169.68	7.265%	$182.0073	$182.01	$182.00	$182.00
Purchase #3	$226.59	6.618%	$241.5857	$241.59	$241.60	$241.60
Purchase #4	$93.31	7.233%	$100.0591	$100.06	$100.05	$100.10
Purchase #5	$179.45	5.123%	$188.6432	$188.64	$188.65	$188.60
Purchase #6	$127.67	8.604%	$138.6547	$138.65	$138.65	$138.70
Purchase #7	$149.82	11.554%	$167.1302	$167.13	$167.15	$167.10
7 purchase totals =	$1,100.91		$1,179.4625	$1,179.46	$1,179.50	$1,179.50