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	$106.31	5.183%	$111.82	$111.82	$111.80	$111.80
Purchase #2	$97.26	6.226%	$103.3154	$103.32	$103.30	$103.30
Purchase #3	$168.95	3.861%	$175.4732	$175.47	$175.45	$175.50
Purchase #4	$119.73	3.572%	$124.0068	$124.01	$124.00	$124.00
Purchase #5	$14.92	8.442%	$16.1795	$16.18	$16.20	$16.20
Purchase #6	$41.61	12.748%	$46.9144	$46.91	$46.90	$46.90
Purchase #7	$143.98	10.363%	$158.9006	$158.90	$158.90	$158.90
7 purchase totals =	$692.76		$736.6099	$736.61	$736.55	$736.60