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	$174.28	11.663%	$194.6063	$194.61	$194.60	$194.60
Purchase #2	$45.42	6.821%	$48.5181	$48.52	$48.50	$48.50
Purchase #3	$46.33	12.278%	$52.0184	$52.02	$52.00	$52.00
Purchase #4	$20.76	6.680%	$22.1468	$22.15	$22.15	$22.10
Purchase #5	$74.30	10.852%	$82.363	$82.36	$82.35	$82.40
Purchase #6	$39.96	6.287%	$42.4723	$42.47	$42.45	$42.50
Purchase #7	$162.54	6.586%	$173.2449	$173.24	$173.25	$173.20
7 purchase totals =	$563.59		$615.3698	$615.37	$615.30	$615.30