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	$164.75	5.244%	$173.3895	$173.39	$173.40	$173.40
Purchase #2	$49.74	10.117%	$54.7722	$54.77	$54.75	$54.80
Purchase #3	$38.55	5.142%	$40.5322	$40.53	$40.55	$40.50
Purchase #4	$218.79	10.233%	$241.1788	$241.18	$241.20	$241.20
Purchase #5	$101.83	7.654%	$109.6241	$109.62	$109.60	$109.60
Purchase #6	$29.97	12.383%	$33.6812	$33.68	$33.70	$33.70
Purchase #7	$96.40	3.111%	$99.399	$99.40	$99.40	$99.40
7 purchase totals =	$700.03		$752.5770	$752.57	$752.60	$752.60