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	$50.62	6.813%	$54.0687	$54.07	$54.05	$54.10
Purchase #2	$14.68	9.543%	$16.0809	$16.08	$16.10	$16.10
Purchase #3	$13.60	6.818%	$14.5272	$14.53	$14.55	$14.50
Purchase #4	$31.25	4.267%	$32.5834	$32.58	$32.60	$32.60
Purchase #5	$154.37	5.150%	$162.3201	$162.32	$162.30	$162.30
Purchase #6	$144.47	13.120%	$163.4245	$163.42	$163.40	$163.40
Purchase #7	$83.78	7.185%	$89.7996	$89.80	$89.80	$89.80
7 purchase totals =	$492.77		$532.8044	$532.80	$532.80	$532.80