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	$41.87	4.346%	$43.6897	$43.69	$43.70	$43.70
Purchase #2	$189.37	7.245%	$203.0899	$203.09	$203.10	$203.10
Purchase #3	$233.82	11.156%	$259.905	$259.91	$259.90	$259.90
Purchase #4	$105.51	3.637%	$109.3474	$109.35	$109.35	$109.30
Purchase #5	$223.39	5.323%	$235.281	$235.28	$235.30	$235.30
Purchase #6	$164.39	9.185%	$179.4892	$179.49	$179.50	$179.50
Purchase #7	$222.85	13.791%	$253.5832	$253.58	$253.60	$253.60
7 purchase totals =	$1,181.20		$1,284.3854	$1,284.39	$1,284.45	$1,284.40