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	$100.60	10.567%	$111.2304	$111.23	$111.25	$111.20
Purchase #2	$80.34	5.171%	$84.4944	$84.49	$84.50	$84.50
Purchase #3	$69.31	12.149%	$77.7305	$77.73	$77.75	$77.70
Purchase #4	$26.32	12.105%	$29.506	$29.51	$29.50	$29.50
Purchase #5	$226.95	6.181%	$240.9778	$240.98	$241.00	$241.00
Purchase #6	$50.36	9.649%	$55.2192	$55.22	$55.20	$55.20
Purchase #7	$104.74	6.136%	$111.1668	$111.17	$111.15	$111.20
7 purchase totals =	$658.62		$710.3251	$710.33	$710.35	$710.30