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	$100.96	8.608%	$109.6506	$109.65	$109.65	$109.70
Purchase #2	$172.64	13.430%	$195.8256	$195.83	$195.85	$195.80
Purchase #3	$32.30	6.635%	$34.4431	$34.44	$34.45	$34.40
Purchase #4	$159.65	3.151%	$164.6806	$164.68	$164.70	$164.70
Purchase #5	$182.81	3.429%	$189.0786	$189.08	$189.10	$189.10
Purchase #6	$145.82	13.253%	$165.1455	$165.15	$165.15	$165.10
Purchase #7	$155.44	3.236%	$160.47	$160.47	$160.45	$160.50
7 purchase totals =	$949.62		$1,019.2940	$1,019.30	$1,019.35	$1,019.30