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	$135.96	4.778%	$142.4562	$142.46	$142.45	$142.50
Purchase #2	$178.29	10.145%	$196.3775	$196.38	$196.40	$196.40
Purchase #3	$184.35	7.183%	$197.5919	$197.59	$197.60	$197.60
Purchase #4	$146.46	8.236%	$158.5224	$158.52	$158.50	$158.50
Purchase #5	$120.74	5.519%	$127.4036	$127.40	$127.40	$127.40
Purchase #6	$60.88	5.318%	$64.1176	$64.12	$64.10	$64.10
Purchase #7	$164.46	9.572%	$180.2021	$180.20	$180.20	$180.20
7 purchase totals =	$991.14		$1,066.6713	$1,066.67	$1,066.65	$1,066.70