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	$173.33	10.283%	$191.1535	$191.15	$191.15	$191.20
Purchase #2	$128.32	7.667%	$138.1583	$138.16	$138.15	$138.20
Purchase #3	$177.31	10.795%	$196.4506	$196.45	$196.45	$196.50
Purchase #4	$68.49	5.627%	$72.3439	$72.34	$72.35	$72.30
Purchase #5	$223.87	4.803%	$234.6225	$234.62	$234.60	$234.60
Purchase #6	$201.53	11.103%	$223.9059	$223.91	$223.90	$223.90
Purchase #7	$153.84	9.382%	$168.2733	$168.27	$168.25	$168.30
7 purchase totals =	$1,126.69		$1,224.9080	$1,224.90	$1,224.85	$1,225.00