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	$147.38	12.252%	$165.437	$165.44	$165.45	$165.40
Purchase #2	$85.59	6.856%	$91.4581	$91.46	$91.45	$91.50
Purchase #3	$103.25	6.519%	$109.9809	$109.98	$110.00	$110.00
Purchase #4	$234.91	7.629%	$252.8313	$252.83	$252.85	$252.80
Purchase #5	$116.90	5.588%	$123.4324	$123.43	$123.45	$123.40
Purchase #6	$141.34	9.467%	$154.7207	$154.72	$154.70	$154.70
Purchase #7	$66.41	5.766%	$70.2392	$70.24	$70.25	$70.20
7 purchase totals =	$895.78		$968.0996	$968.10	$968.15	$968.00