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	$249.47	10.525%	$275.7267	$275.73	$275.75	$275.70
Purchase #2	$100.46	12.114%	$112.6297	$112.63	$112.65	$112.60
Purchase #3	$66.82	5.668%	$70.6074	$70.61	$70.60	$70.60
Purchase #4	$59.70	12.465%	$67.1416	$67.14	$67.15	$67.10
Purchase #5	$158.71	9.323%	$173.5065	$173.51	$173.50	$173.50
Purchase #6	$133.63	6.640%	$142.503	$142.50	$142.50	$142.50
Purchase #7	$206.63	11.730%	$230.8677	$230.87	$230.85	$230.90
7 purchase totals =	$975.42		$1,072.9826	$1,072.99	$1,073.00	$1,072.90