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	$60.99	3.719%	$63.2582	$63.26	$63.25	$63.30
Purchase #2	$55.83	6.445%	$59.4282	$59.43	$59.45	$59.40
Purchase #3	$62.43	3.867%	$64.8442	$64.84	$64.85	$64.80
Purchase #4	$72.95	4.253%	$76.0526	$76.05	$76.05	$76.10
Purchase #5	$5.27	10.723%	$5.8351	$5.84	$5.85	$5.80
Purchase #6	$40.67	6.697%	$43.3937	$43.39	$43.40	$43.40
Purchase #7	$150.73	9.555%	$165.1323	$165.13	$165.15	$165.10
7 purchase totals =	$448.87		$477.9443	$477.94	$478.00	$477.90