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	$170.84	6.609%	$182.1308	$182.13	$182.15	$182.10
Purchase #2	$131.79	5.828%	$139.4707	$139.47	$139.45	$139.50
Purchase #3	$76.76	3.131%	$79.1634	$79.16	$79.15	$79.20
Purchase #4	$104.71	4.379%	$109.2953	$109.30	$109.30	$109.30
Purchase #5	$211.96	5.560%	$223.745	$223.75	$223.75	$223.70
Purchase #6	$134.75	10.243%	$148.5524	$148.55	$148.55	$148.60
Purchase #7	$164.65	13.635%	$187.1	$187.10	$187.10	$187.10
7 purchase totals =	$995.46		$1,069.4576	$1,069.46	$1,069.45	$1,069.50