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	$79.65	3.699%	$82.5963	$82.60	$82.60	$82.60
Purchase #2	$178.91	4.758%	$187.4225	$187.42	$187.40	$187.40
Purchase #3	$209.80	6.418%	$223.265	$223.27	$223.25	$223.30
Purchase #4	$191.69	6.811%	$204.746	$204.75	$204.75	$204.70
Purchase #5	$118.65	4.325%	$123.7816	$123.78	$123.80	$123.80
Purchase #6	$214.78	8.504%	$233.0449	$233.04	$233.05	$233.00
Purchase #7	$142.86	11.237%	$158.9132	$158.91	$158.90	$158.90
7 purchase totals =	$1,136.34		$1,213.7695	$1,213.77	$1,213.75	$1,213.70