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	$153.45	3.254%	$158.4433	$158.44	$158.45	$158.40
Purchase #2	$116.75	10.180%	$128.6352	$128.64	$128.65	$128.60
Purchase #3	$176.73	8.667%	$192.0472	$192.05	$192.05	$192.00
Purchase #4	$39.59	4.608%	$41.4143	$41.41	$41.40	$41.40
Purchase #5	$208.85	3.236%	$215.6084	$215.61	$215.60	$215.60
Purchase #6	$75.52	13.801%	$85.9425	$85.94	$85.95	$85.90
Purchase #7	$247.40	12.604%	$278.5823	$278.58	$278.60	$278.60
7 purchase totals =	$1,018.29		$1,100.6732	$1,100.67	$1,100.70	$1,100.50