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	$182.83	12.578%	$205.8264	$205.83	$205.85	$205.80
Purchase #2	$89.45	12.789%	$100.8898	$100.89	$100.90	$100.90
Purchase #3	$61.79	11.653%	$68.9904	$68.99	$69.00	$69.00
Purchase #4	$151.84	10.840%	$168.2995	$168.30	$168.30	$168.30
Purchase #5	$30.33	12.651%	$34.167	$34.17	$34.15	$34.20
Purchase #6	$105.80	5.388%	$111.5005	$111.50	$111.50	$111.50
Purchase #7	$32.31	12.509%	$36.3517	$36.35	$36.35	$36.40
7 purchase totals =	$654.35		$726.0253	$726.03	$726.05	$726.10