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	$80.89	6.567%	$86.202	$86.20	$86.20	$86.20
Purchase #2	$226.88	6.658%	$241.9857	$241.99	$242.00	$242.00
Purchase #3	$46.51	10.341%	$51.3196	$51.32	$51.30	$51.30
Purchase #4	$99.89	11.227%	$111.1047	$111.10	$111.10	$111.10
Purchase #5	$179.35	11.846%	$200.5958	$200.60	$200.60	$200.60
Purchase #6	$191.95	6.340%	$204.1196	$204.12	$204.10	$204.10
Purchase #7	$56.75	10.375%	$62.6378	$62.64	$62.65	$62.60
7 purchase totals =	$882.22		$957.9652	$957.97	$957.95	$957.90