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	$178.80	8.388%	$193.7977	$193.80	$193.80	$193.80
Purchase #2	$65.62	3.170%	$67.7002	$67.70	$67.70	$67.70
Purchase #3	$188.47	13.727%	$214.3413	$214.34	$214.35	$214.30
Purchase #4	$131.34	4.661%	$137.4618	$137.46	$137.45	$137.50
Purchase #5	$128.82	11.444%	$143.5622	$143.56	$143.55	$143.60
Purchase #6	$176.28	11.545%	$196.6315	$196.63	$196.65	$196.60
Purchase #7	$178.92	11.867%	$200.1524	$200.15	$200.15	$200.20
7 purchase totals =	$1,048.25		$1,153.6471	$1,153.64	$1,153.65	$1,153.70