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	$232.96	10.693%	$257.8704	$257.87	$257.85	$257.90
Purchase #2	$202.34	8.397%	$219.3305	$219.33	$219.35	$219.30
Purchase #3	$98.92	13.137%	$111.9151	$111.92	$111.90	$111.90
Purchase #4	$223.25	3.389%	$230.8159	$230.82	$230.80	$230.80
Purchase #5	$15.98	6.183%	$16.968	$16.97	$16.95	$17.00
Purchase #6	$172.26	9.439%	$188.5196	$188.52	$188.50	$188.50
Purchase #7	$70.30	3.714%	$72.9109	$72.91	$72.90	$72.90
7 purchase totals =	$1,016.01		$1,098.3304	$1,098.34	$1,098.25	$1,098.30