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	$54.91	10.615%	$60.7387	$60.74	$60.75	$60.70
Purchase #2	$224.29	8.742%	$243.8974	$243.90	$243.90	$243.90
Purchase #3	$94.32	11.189%	$104.8735	$104.87	$104.85	$104.90
Purchase #4	$79.62	10.694%	$88.1346	$88.13	$88.15	$88.10
Purchase #5	$91.78	12.255%	$103.0276	$103.03	$103.05	$103.00
Purchase #6	$107.35	4.215%	$111.8748	$111.87	$111.85	$111.90
Purchase #7	$220.46	13.531%	$250.2904	$250.29	$250.30	$250.30
7 purchase totals =	$872.73		$962.8370	$962.83	$962.85	$962.80