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	$164.68	4.607%	$172.2668	$172.27	$172.25	$172.30
Purchase #2	$190.91	5.201%	$200.8392	$200.84	$200.85	$200.80
Purchase #3	$223.72	3.441%	$231.4182	$231.42	$231.40	$231.40
Purchase #4	$103.45	9.843%	$113.6326	$113.63	$113.65	$113.60
Purchase #5	$188.39	6.242%	$200.1493	$200.15	$200.15	$200.10
Purchase #6	$198.81	13.300%	$225.2517	$225.25	$225.25	$225.30
Purchase #7	$175.54	11.399%	$195.5498	$195.55	$195.55	$195.50
7 purchase totals =	$1,245.50		$1,339.1076	$1,339.11	$1,339.10	$1,339.00