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	$41.26	11.163%	$45.8659	$45.87	$45.85	$45.90
Purchase #2	$246.37	6.652%	$262.7585	$262.76	$262.75	$262.80
Purchase #3	$68.82	5.124%	$72.3463	$72.35	$72.35	$72.30
Purchase #4	$210.29	5.804%	$222.4952	$222.50	$222.50	$222.50
Purchase #5	$146.35	8.256%	$158.4327	$158.43	$158.45	$158.40
Purchase #6	$134.29	6.250%	$142.6831	$142.68	$142.70	$142.70
Purchase #7	$233.32	13.861%	$265.6605	$265.66	$265.65	$265.70
7 purchase totals =	$1,080.70		$1,170.2422	$1,170.25	$1,170.25	$1,170.30