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	$56.46	8.670%	$61.3551	$61.36	$61.35	$61.40
Purchase #2	$83.42	5.823%	$88.2775	$88.28	$88.30	$88.30
Purchase #3	$114.65	7.624%	$123.3909	$123.39	$123.40	$123.40
Purchase #4	$63.35	12.844%	$71.4867	$71.49	$71.50	$71.50
Purchase #5	$175.60	3.728%	$182.1464	$182.15	$182.15	$182.10
Purchase #6	$172.47	9.443%	$188.7563	$188.76	$188.75	$188.80
Purchase #7	$164.82	8.395%	$178.6566	$178.66	$178.65	$178.70
7 purchase totals =	$830.77		$894.0695	$894.09	$894.10	$894.20