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	$156.40	3.573%	$161.9882	$161.99	$162.00	$162.00
Purchase #2	$238.55	11.267%	$265.4274	$265.43	$265.45	$265.40
Purchase #3	$73.39	12.575%	$82.6188	$82.62	$82.60	$82.60
Purchase #4	$133.54	13.395%	$151.4277	$151.43	$151.45	$151.40
Purchase #5	$70.77	10.453%	$78.1676	$78.17	$78.15	$78.20
Purchase #6	$173.98	8.325%	$188.4638	$188.46	$188.45	$188.50
Purchase #7	$154.45	3.500%	$159.8558	$159.86	$159.85	$159.90
7 purchase totals =	$1,001.08		$1,087.9493	$1,087.96	$1,087.95	$1,088.00