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	$54.28	9.855%	$59.6293	$59.63	$59.65	$59.60
Purchase #2	$34.84	6.380%	$37.0628	$37.06	$37.05	$37.10
Purchase #3	$114.78	11.370%	$127.8305	$127.83	$127.85	$127.80
Purchase #4	$229.29	5.670%	$242.2907	$242.29	$242.30	$242.30
Purchase #5	$188.69	8.323%	$204.3947	$204.39	$204.40	$204.40
Purchase #6	$84.35	7.221%	$90.4409	$90.44	$90.45	$90.40
Purchase #7	$14.62	5.612%	$15.4405	$15.44	$15.45	$15.40
7 purchase totals =	$720.85		$777.0894	$777.08	$777.15	$777.00