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	$244.29	9.838%	$268.3233	$268.32	$268.30	$268.30
Purchase #2	$54.68	3.382%	$56.5293	$56.53	$56.55	$56.50
Purchase #3	$17.68	7.464%	$18.9996	$19.00	$19.00	$19.00
Purchase #4	$181.37	8.428%	$196.6559	$196.66	$196.65	$196.70
Purchase #5	$160.38	7.592%	$172.556	$172.56	$172.55	$172.60
Purchase #6	$111.76	13.189%	$126.5	$126.50	$126.50	$126.50
Purchase #7	$188.59	8.643%	$204.8898	$204.89	$204.90	$204.90
7 purchase totals =	$958.75		$1,044.4539	$1,044.46	$1,044.45	$1,044.50