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	$212.76	10.593%	$235.2977	$235.30	$235.30	$235.30
Purchase #2	$58.45	5.252%	$61.5198	$61.52	$61.50	$61.50
Purchase #3	$150.58	5.119%	$158.2882	$158.29	$158.30	$158.30
Purchase #4	$102.31	3.369%	$105.7568	$105.76	$105.75	$105.80
Purchase #5	$248.73	9.775%	$273.0434	$273.04	$273.05	$273.00
Purchase #6	$179.54	6.605%	$191.3986	$191.40	$191.40	$191.40
Purchase #7	$184.41	7.117%	$197.5345	$197.53	$197.55	$197.50
7 purchase totals =	$1,136.78		$1,222.8390	$1,222.84	$1,222.85	$1,222.80