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	$112.55	13.485%	$127.7274	$127.73	$127.75	$127.70
Purchase #2	$114.54	6.629%	$122.1329	$122.13	$122.15	$122.10
Purchase #3	$7.43	3.820%	$7.7138	$7.71	$7.70	$7.70
Purchase #4	$104.66	11.270%	$116.4552	$116.46	$116.45	$116.50
Purchase #5	$172.32	9.146%	$188.0804	$188.08	$188.10	$188.10
Purchase #6	$29.65	4.722%	$31.0501	$31.05	$31.05	$31.10
Purchase #7	$34.25	10.202%	$37.7442	$37.74	$37.75	$37.70
7 purchase totals =	$575.40		$630.9040	$630.90	$630.95	$630.90