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	$150.71	13.278%	$170.7213	$170.72	$170.70	$170.70
Purchase #2	$167.98	3.137%	$173.2495	$173.25	$173.25	$173.20
Purchase #3	$55.83	9.498%	$61.1327	$61.13	$61.15	$61.10
Purchase #4	$189.32	8.484%	$205.3819	$205.38	$205.40	$205.40
Purchase #5	$51.44	6.872%	$54.975	$54.98	$55.00	$55.00
Purchase #6	$92.62	12.782%	$104.4587	$104.46	$104.45	$104.50
Purchase #7	$158.42	8.729%	$172.2485	$172.25	$172.25	$172.20
7 purchase totals =	$866.32		$942.1676	$942.17	$942.20	$942.10