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	$164.27	4.763%	$172.0942	$172.09	$172.10	$172.10
Purchase #2	$113.69	9.792%	$124.8225	$124.82	$124.80	$124.80
Purchase #3	$184.45	3.865%	$191.579	$191.58	$191.60	$191.60
Purchase #4	$127.74	13.221%	$144.6285	$144.63	$144.65	$144.60
Purchase #5	$245.61	8.476%	$266.4279	$266.43	$266.45	$266.40
Purchase #6	$66.75	10.569%	$73.8048	$73.80	$73.80	$73.80
Purchase #7	$171.97	4.199%	$179.191	$179.19	$179.20	$179.20
7 purchase totals =	$1,074.48		$1,152.5479	$1,152.54	$1,152.60	$1,152.50