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	$157.84	9.223%	$172.3976	$172.40	$172.40	$172.40
Purchase #2	$224.29	5.742%	$237.1687	$237.17	$237.15	$237.20
Purchase #3	$211.35	9.256%	$230.9126	$230.91	$230.90	$230.90
Purchase #4	$17.68	4.369%	$18.4524	$18.45	$18.45	$18.50
Purchase #5	$79.89	4.208%	$83.2518	$83.25	$83.25	$83.30
Purchase #6	$144.71	3.732%	$150.1106	$150.11	$150.10	$150.10
Purchase #7	$152.42	4.593%	$159.4207	$159.42	$159.40	$159.40
7 purchase totals =	$988.18		$1,051.7144	$1,051.71	$1,051.65	$1,051.80