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	$76.45	12.357%	$85.8969	$85.90	$85.90	$85.90
Purchase #2	$6.85	3.457%	$7.0868	$7.09	$7.10	$7.10
Purchase #3	$89.94	10.723%	$99.5843	$99.58	$99.60	$99.60
Purchase #4	$62.61	4.866%	$65.6566	$65.66	$65.65	$65.70
Purchase #5	$82.30	9.447%	$90.0749	$90.07	$90.05	$90.10
Purchase #6	$127.95	10.272%	$141.093	$141.09	$141.10	$141.10
Purchase #7	$58.50	13.146%	$66.1904	$66.19	$66.20	$66.20
7 purchase totals =	$504.60		$555.5829	$555.58	$555.60	$555.70