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	$96.35	13.773%	$109.6203	$109.62	$109.60	$109.60
Purchase #2	$102.36	3.435%	$105.8761	$105.88	$105.90	$105.90
Purchase #3	$148.87	6.473%	$158.5064	$158.51	$158.50	$158.50
Purchase #4	$134.65	7.606%	$144.8915	$144.89	$144.90	$144.90
Purchase #5	$222.77	3.324%	$230.1749	$230.17	$230.15	$230.20
Purchase #6	$249.78	11.790%	$279.2291	$279.23	$279.25	$279.20
Purchase #7	$237.84	6.672%	$253.7087	$253.71	$253.70	$253.70
7 purchase totals =	$1,192.62		$1,282.0070	$1,282.01	$1,282.00	$1,282.00