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	$158.52	7.717%	$170.753	$170.75	$170.75	$170.80
Purchase #2	$53.47	8.377%	$57.9492	$57.95	$57.95	$57.90
Purchase #3	$48.88	4.113%	$50.8904	$50.89	$50.90	$50.90
Purchase #4	$96.54	9.234%	$105.4545	$105.45	$105.45	$105.50
Purchase #5	$32.54	12.181%	$36.5037	$36.50	$36.50	$36.50
Purchase #6	$9.93	4.789%	$10.4055	$10.41	$10.40	$10.40
Purchase #7	$138.67	3.832%	$143.9838	$143.98	$144.00	$144.00
7 purchase totals =	$538.55		$575.9401	$575.93	$575.95	$576.00