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	$67.54	9.805%	$74.1623	$74.16	$74.15	$74.20
Purchase #2	$154.26	3.361%	$159.4447	$159.44	$159.45	$159.40
Purchase #3	$230.80	13.740%	$262.5119	$262.51	$262.50	$262.50
Purchase #4	$169.77	12.779%	$191.4649	$191.46	$191.45	$191.50
Purchase #5	$74.79	5.388%	$78.8197	$78.82	$78.80	$78.80
Purchase #6	$173.93	3.867%	$180.6559	$180.66	$180.65	$180.70
Purchase #7	$96.86	6.777%	$103.4242	$103.42	$103.40	$103.40
7 purchase totals =	$967.95		$1,050.4836	$1,050.47	$1,050.40	$1,050.50