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	$39.98	3.573%	$41.4085	$41.41	$41.40	$41.40
Purchase #2	$79.97	11.420%	$89.1026	$89.10	$89.10	$89.10
Purchase #3	$15.88	10.545%	$17.5545	$17.55	$17.55	$17.60
Purchase #4	$227.83	11.577%	$254.2059	$254.21	$254.20	$254.20
Purchase #5	$89.69	6.471%	$95.4938	$95.49	$95.50	$95.50
Purchase #6	$47.31	4.434%	$49.4077	$49.41	$49.40	$49.40
Purchase #7	$196.52	11.509%	$219.1375	$219.14	$219.15	$219.10
7 purchase totals =	$697.18		$766.3105	$766.31	$766.30	$766.30