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	$62.42	8.321%	$67.614	$67.61	$67.60	$67.60
Purchase #2	$149.85	10.309%	$165.298	$165.30	$165.30	$165.30
Purchase #3	$9.39	11.823%	$10.5002	$10.50	$10.50	$10.50
Purchase #4	$44.88	12.789%	$50.6197	$50.62	$50.60	$50.60
Purchase #5	$36.52	4.774%	$38.2635	$38.26	$38.25	$38.30
Purchase #6	$49.98	7.732%	$53.8445	$53.84	$53.85	$53.80
Purchase #7	$250.29	3.698%	$259.5457	$259.55	$259.55	$259.50
7 purchase totals =	$603.33		$645.6856	$645.68	$645.65	$645.60