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	$214.90	11.377%	$239.3492	$239.35	$239.35	$239.30
Purchase #2	$112.61	7.114%	$120.6211	$120.62	$120.60	$120.60
Purchase #3	$134.52	12.151%	$150.8655	$150.87	$150.85	$150.90
Purchase #4	$111.49	3.640%	$115.5482	$115.55	$115.55	$115.50
Purchase #5	$198.76	12.174%	$222.957	$222.96	$222.95	$223.00
Purchase #6	$190.49	6.802%	$203.4471	$203.45	$203.45	$203.40
Purchase #7	$233.44	9.615%	$255.8853	$255.89	$255.90	$255.90
7 purchase totals =	$1,196.21		$1,308.6734	$1,308.69	$1,308.65	$1,308.60