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	$145.80	13.518%	$165.5092	$165.51	$165.50	$165.50
Purchase #2	$176.78	10.668%	$195.6389	$195.64	$195.65	$195.60
Purchase #3	$180.88	8.363%	$196.007	$196.01	$196.00	$196.00
Purchase #4	$115.49	13.476%	$131.0534	$131.05	$131.05	$131.10
Purchase #5	$163.56	5.243%	$172.1355	$172.14	$172.15	$172.10
Purchase #6	$121.88	5.144%	$128.1495	$128.15	$128.15	$128.10
Purchase #7	$104.30	11.846%	$116.6554	$116.66	$116.65	$116.70
7 purchase totals =	$1,008.69		$1,105.1489	$1,105.16	$1,105.15	$1,105.10