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	$21.49	12.347%	$24.1434	$24.14	$24.15	$24.10
Purchase #2	$92.57	5.866%	$98.0002	$98.00	$98.00	$98.00
Purchase #3	$134.95	5.707%	$142.6516	$142.65	$142.65	$142.70
Purchase #4	$32.62	12.714%	$36.7673	$36.77	$36.75	$36.80
Purchase #5	$35.94	5.804%	$38.026	$38.03	$38.05	$38.00
Purchase #6	$78.80	13.323%	$89.2985	$89.30	$89.30	$89.30
Purchase #7	$52.82	12.670%	$59.5123	$59.51	$59.50	$59.50
7 purchase totals =	$449.19		$488.3993	$488.40	$488.40	$488.40