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	$26.76	10.398%	$29.5425	$29.54	$29.55	$29.50
Purchase #2	$224.69	13.749%	$255.5826	$255.58	$255.60	$255.60
Purchase #3	$86.88	9.750%	$95.3508	$95.35	$95.35	$95.40
Purchase #4	$183.44	9.312%	$200.5219	$200.52	$200.50	$200.50
Purchase #5	$194.90	4.807%	$204.2688	$204.27	$204.25	$204.30
Purchase #6	$248.73	9.331%	$271.939	$271.94	$271.95	$271.90
Purchase #7	$105.88	5.321%	$111.5139	$111.51	$111.50	$111.50
7 purchase totals =	$1,071.28		$1,168.7195	$1,168.71	$1,168.70	$1,168.70