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	$172.50	12.259%	$193.6468	$193.65	$193.65	$193.60
Purchase #2	$54.34	7.487%	$58.4084	$58.41	$58.40	$58.40
Purchase #3	$146.26	4.537%	$152.8958	$152.90	$152.90	$152.90
Purchase #4	$59.60	11.818%	$66.6435	$66.64	$66.65	$66.60
Purchase #5	$92.85	8.516%	$100.7571	$100.76	$100.75	$100.80
Purchase #6	$171.34	7.823%	$184.7439	$184.74	$184.75	$184.70
Purchase #7	$129.35	11.650%	$144.4193	$144.42	$144.40	$144.40
7 purchase totals =	$826.24		$901.5148	$901.52	$901.50	$901.40