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	$68.61	5.544%	$72.4137	$72.41	$72.40	$72.40
Purchase #2	$44.88	13.374%	$50.8823	$50.88	$50.90	$50.90
Purchase #3	$32.92	6.135%	$34.9396	$34.94	$34.95	$34.90
Purchase #4	$92.55	10.262%	$102.0475	$102.05	$102.05	$102.00
Purchase #5	$156.80	3.723%	$162.6377	$162.64	$162.65	$162.60
Purchase #6	$92.49	4.353%	$96.5161	$96.52	$96.50	$96.50
Purchase #7	$158.64	8.478%	$172.0895	$172.09	$172.10	$172.10
7 purchase totals =	$646.89		$691.5264	$691.53	$691.55	$691.40