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	$250.33	7.208%	$268.3738	$268.37	$268.35	$268.40
Purchase #2	$173.88	9.613%	$190.5951	$190.60	$190.60	$190.60
Purchase #3	$143.41	13.590%	$162.8994	$162.90	$162.90	$162.90
Purchase #4	$226.91	9.626%	$248.7524	$248.75	$248.75	$248.80
Purchase #5	$57.65	6.209%	$61.2295	$61.23	$61.25	$61.20
Purchase #6	$51.42	13.478%	$58.3504	$58.35	$58.35	$58.40
Purchase #7	$54.79	11.342%	$61.0043	$61.00	$61.00	$61.00
7 purchase totals =	$958.39		$1,051.2049	$1,051.20	$1,051.20	$1,051.30