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	$113.60	12.586%	$127.8977	$127.90	$127.90	$127.90
Purchase #2	$242.52	9.550%	$265.6807	$265.68	$265.70	$265.70
Purchase #3	$222.69	6.603%	$237.3942	$237.39	$237.40	$237.40
Purchase #4	$123.63	13.591%	$140.4326	$140.43	$140.45	$140.40
Purchase #5	$216.58	5.857%	$229.2651	$229.27	$229.25	$229.30
Purchase #6	$141.46	3.608%	$146.5639	$146.56	$146.55	$146.60
Purchase #7	$64.45	11.137%	$71.6278	$71.63	$71.65	$71.60
7 purchase totals =	$1,124.93		$1,218.8620	$1,218.86	$1,218.90	$1,218.90