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	$244.30	5.657%	$258.1201	$258.12	$258.10	$258.10
Purchase #2	$209.54	12.341%	$235.3993	$235.40	$235.40	$235.40
Purchase #3	$226.97	9.645%	$248.8613	$248.86	$248.85	$248.90
Purchase #4	$100.90	10.314%	$111.3068	$111.31	$111.30	$111.30
Purchase #5	$78.72	13.662%	$89.4747	$89.47	$89.45	$89.50
Purchase #6	$28.42	7.615%	$30.5842	$30.58	$30.60	$30.60
Purchase #7	$65.66	4.658%	$68.7184	$68.72	$68.70	$68.70
7 purchase totals =	$954.51		$1,042.4648	$1,042.46	$1,042.40	$1,042.50