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	$242.90	13.471%	$275.6211	$275.62	$275.60	$275.60
Purchase #2	$192.37	8.629%	$208.9696	$208.97	$208.95	$209.00
Purchase #3	$204.64	5.325%	$215.5371	$215.54	$215.55	$215.50
Purchase #4	$107.75	8.578%	$116.9928	$116.99	$117.00	$117.00
Purchase #5	$133.76	7.845%	$144.2535	$144.25	$144.25	$144.30
Purchase #6	$79.77	3.505%	$82.5659	$82.57	$82.55	$82.60
Purchase #7	$143.88	5.814%	$152.2452	$152.25	$152.25	$152.20
7 purchase totals =	$1,105.07		$1,196.1852	$1,196.19	$1,196.15	$1,196.20