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	$167.48	3.209%	$172.8544	$172.85	$172.85	$172.90
Purchase #2	$158.34	13.426%	$179.5987	$179.60	$179.60	$179.60
Purchase #3	$37.70	6.250%	$40.0563	$40.06	$40.05	$40.10
Purchase #4	$5.48	13.521%	$6.221	$6.22	$6.20	$6.20
Purchase #5	$194.65	7.613%	$209.4687	$209.47	$209.45	$209.50
Purchase #6	$204.30	5.255%	$215.036	$215.04	$215.05	$215.00
Purchase #7	$33.32	13.589%	$37.8479	$37.85	$37.85	$37.80
7 purchase totals =	$801.27		$861.0830	$861.09	$861.05	$861.10