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	$241.56	5.606%	$255.1019	$255.10	$255.10	$255.10
Purchase #2	$74.69	10.279%	$82.3674	$82.37	$82.35	$82.40
Purchase #3	$214.55	6.590%	$228.6888	$228.69	$228.70	$228.70
Purchase #4	$245.98	10.622%	$272.108	$272.11	$272.10	$272.10
Purchase #5	$130.57	7.224%	$140.0024	$140.00	$140.00	$140.00
Purchase #6	$48.86	8.733%	$53.1269	$53.13	$53.15	$53.10
Purchase #7	$151.28	9.364%	$165.4459	$165.45	$165.45	$165.40
7 purchase totals =	$1,107.49		$1,196.8413	$1,196.85	$1,196.85	$1,196.80