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	$140.73	4.140%	$146.5562	$146.56	$146.55	$146.60
Purchase #2	$38.86	4.496%	$40.6071	$40.61	$40.60	$40.60
Purchase #3	$141.96	6.809%	$151.6261	$151.63	$151.65	$151.60
Purchase #4	$170.85	3.160%	$176.2489	$176.25	$176.25	$176.20
Purchase #5	$217.98	5.325%	$229.5874	$229.59	$229.60	$229.60
Purchase #6	$104.56	6.384%	$111.2351	$111.24	$111.25	$111.20
Purchase #7	$203.49	9.153%	$222.1154	$222.12	$222.10	$222.10
7 purchase totals =	$1,018.43		$1,077.9762	$1,078.00	$1,078.00	$1,077.90