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	$249.61	5.459%	$263.2362	$263.24	$263.25	$263.20
Purchase #2	$72.59	7.671%	$78.1584	$78.16	$78.15	$78.20
Purchase #3	$191.78	7.211%	$205.6093	$205.61	$205.60	$205.60
Purchase #4	$79.37	5.381%	$83.6409	$83.64	$83.65	$83.60
Purchase #5	$218.70	6.852%	$233.6853	$233.69	$233.70	$233.70
Purchase #6	$221.97	5.731%	$234.6911	$234.69	$234.70	$234.70
Purchase #7	$138.38	13.766%	$157.4294	$157.43	$157.45	$157.40
7 purchase totals =	$1,172.40		$1,256.4506	$1,256.46	$1,256.50	$1,256.40