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	$137.61	10.665%	$152.2861	$152.29	$152.30	$152.30
Purchase #2	$192.98	7.845%	$208.1193	$208.12	$208.10	$208.10
Purchase #3	$214.49	4.102%	$223.2884	$223.29	$223.30	$223.30
Purchase #4	$129.94	9.311%	$142.0387	$142.04	$142.05	$142.00
Purchase #5	$228.53	11.690%	$255.2452	$255.25	$255.25	$255.20
Purchase #6	$118.76	5.106%	$124.8239	$124.82	$124.80	$124.80
Purchase #7	$121.35	5.771%	$128.3531	$128.35	$128.35	$128.40
7 purchase totals =	$1,143.66		$1,234.1547	$1,234.16	$1,234.15	$1,234.10