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	$222.82	4.774%	$233.4574	$233.46	$233.45	$233.50
Purchase #2	$200.78	12.407%	$225.6908	$225.69	$225.70	$225.70
Purchase #3	$207.53	7.680%	$223.4683	$223.47	$223.45	$223.50
Purchase #4	$11.90	11.493%	$13.2677	$13.27	$13.25	$13.30
Purchase #5	$231.43	13.708%	$263.1544	$263.15	$263.15	$263.20
Purchase #6	$179.30	7.489%	$192.7278	$192.73	$192.75	$192.70
Purchase #7	$226.40	12.553%	$254.82	$254.82	$254.80	$254.80
7 purchase totals =	$1,280.16		$1,406.5864	$1,406.59	$1,406.55	$1,406.70