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	$102.51	13.118%	$115.9573	$115.96	$115.95	$116.00
Purchase #2	$118.61	10.426%	$130.9763	$130.98	$131.00	$131.00
Purchase #3	$99.32	3.540%	$102.8359	$102.84	$102.85	$102.80
Purchase #4	$105.77	5.841%	$111.948	$111.95	$111.95	$111.90
Purchase #5	$50.75	6.449%	$54.0229	$54.02	$54.00	$54.00
Purchase #6	$154.94	6.541%	$165.0746	$165.07	$165.05	$165.10
Purchase #7	$198.70	8.173%	$214.9398	$214.94	$214.95	$214.90
7 purchase totals =	$830.60		$895.7548	$895.76	$895.75	$895.70