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	$138.84	5.509%	$146.4887	$146.49	$146.50	$146.50
Purchase #2	$176.92	8.139%	$191.3195	$191.32	$191.30	$191.30
Purchase #3	$115.45	8.207%	$124.925	$124.93	$124.95	$124.90
Purchase #4	$222.26	4.765%	$232.8507	$232.85	$232.85	$232.90
Purchase #5	$170.37	5.378%	$179.5325	$179.53	$179.55	$179.50
Purchase #6	$146.93	10.724%	$162.6868	$162.69	$162.70	$162.70
Purchase #7	$100.62	10.336%	$111.0201	$111.02	$111.00	$111.00
7 purchase totals =	$1,071.39		$1,148.8233	$1,148.83	$1,148.85	$1,148.80