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	$66.42	13.267%	$75.2319	$75.23	$75.25	$75.20
Purchase #2	$152.57	7.445%	$163.9288	$163.93	$163.95	$163.90
Purchase #3	$57.80	13.156%	$65.4042	$65.40	$65.40	$65.40
Purchase #4	$54.93	8.491%	$59.5941	$59.59	$59.60	$59.60
Purchase #5	$68.98	13.738%	$78.4565	$78.46	$78.45	$78.50
Purchase #6	$199.34	5.619%	$210.5409	$210.54	$210.55	$210.50
Purchase #7	$208.30	10.321%	$229.7986	$229.80	$229.80	$229.80
7 purchase totals =	$808.34		$882.9550	$882.95	$883.00	$882.90