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	$230.86	13.763%	$262.6333	$262.63	$262.65	$262.60
Purchase #2	$157.51	13.728%	$179.133	$179.13	$179.15	$179.10
Purchase #3	$9.83	6.323%	$10.4516	$10.45	$10.45	$10.50
Purchase #4	$180.63	8.803%	$196.5309	$196.53	$196.55	$196.50
Purchase #5	$204.91	3.165%	$211.3954	$211.40	$211.40	$211.40
Purchase #6	$243.59	11.336%	$271.2034	$271.20	$271.20	$271.20
Purchase #7	$112.81	9.700%	$123.7526	$123.75	$123.75	$123.80
7 purchase totals =	$1,140.14		$1,255.1002	$1,255.09	$1,255.15	$1,255.10