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	$153.29	7.639%	$164.9998	$165.00	$165.00	$165.00
Purchase #2	$247.84	12.806%	$279.5784	$279.58	$279.60	$279.60
Purchase #3	$159.25	3.441%	$164.7298	$164.73	$164.75	$164.70
Purchase #4	$176.49	8.874%	$192.1517	$192.15	$192.15	$192.20
Purchase #5	$76.43	6.521%	$81.414	$81.41	$81.40	$81.40
Purchase #6	$46.68	8.183%	$50.4998	$50.50	$50.50	$50.50
Purchase #7	$71.85	9.594%	$78.7433	$78.74	$78.75	$78.70
7 purchase totals =	$931.83		$1,012.1168	$1,012.11	$1,012.15	$1,012.10