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	$80.26	9.741%	$88.0781	$88.08	$88.10	$88.10
Purchase #2	$231.94	10.763%	$256.9037	$256.90	$256.90	$256.90
Purchase #3	$95.67	11.793%	$106.9524	$106.95	$106.95	$107.00
Purchase #4	$106.73	11.337%	$118.83	$118.83	$118.85	$118.80
Purchase #5	$30.79	11.200%	$34.2385	$34.24	$34.25	$34.20
Purchase #6	$74.46	5.563%	$78.6022	$78.60	$78.60	$78.60
Purchase #7	$54.89	6.160%	$58.2712	$58.27	$58.25	$58.30
7 purchase totals =	$674.74		$741.8761	$741.87	$741.90	$741.90