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	$170.42	8.457%	$184.8324	$184.83	$184.85	$184.80
Purchase #2	$181.78	5.766%	$192.2614	$192.26	$192.25	$192.30
Purchase #3	$174.30	4.256%	$181.7182	$181.72	$181.70	$181.70
Purchase #4	$214.25	4.612%	$224.1312	$224.13	$224.15	$224.10
Purchase #5	$76.56	7.511%	$82.3104	$82.31	$82.30	$82.30
Purchase #6	$149.75	3.688%	$155.2728	$155.27	$155.25	$155.30
Purchase #7	$46.82	12.716%	$52.7736	$52.77	$52.75	$52.80
7 purchase totals =	$1,013.88		$1,073.3000	$1,073.29	$1,073.25	$1,073.30