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	$156.84	11.434%	$174.7731	$174.77	$174.75	$174.80
Purchase #2	$181.69	7.295%	$194.9443	$194.94	$194.95	$194.90
Purchase #3	$156.87	10.608%	$173.5108	$173.51	$173.50	$173.50
Purchase #4	$97.26	5.777%	$102.8787	$102.88	$102.90	$102.90
Purchase #5	$100.80	4.635%	$105.4721	$105.47	$105.45	$105.50
Purchase #6	$133.32	8.390%	$144.5055	$144.51	$144.50	$144.50
Purchase #7	$165.25	10.603%	$182.7715	$182.77	$182.75	$182.80
7 purchase totals =	$992.03		$1,078.8560	$1,078.85	$1,078.80	$1,078.90