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	$46.35	13.477%	$52.5966	$52.60	$52.60	$52.60
Purchase #2	$78.37	8.621%	$85.1263	$85.13	$85.15	$85.10
Purchase #3	$216.91	4.587%	$226.8597	$226.86	$226.85	$226.90
Purchase #4	$27.52	13.433%	$31.2168	$31.22	$31.20	$31.20
Purchase #5	$114.63	7.145%	$122.8203	$122.82	$122.80	$122.80
Purchase #6	$38.60	4.729%	$40.4254	$40.43	$40.45	$40.40
Purchase #7	$191.84	6.507%	$204.323	$204.32	$204.30	$204.30
7 purchase totals =	$714.22		$763.3681	$763.38	$763.35	$763.30