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	$62.80	7.830%	$67.7172	$67.72	$67.70	$67.70
Purchase #2	$48.91	3.788%	$50.7627	$50.76	$50.75	$50.80
Purchase #3	$88.86	7.385%	$95.4223	$95.42	$95.40	$95.40
Purchase #4	$14.34	4.527%	$14.9892	$14.99	$15.00	$15.00
Purchase #5	$29.62	5.557%	$31.266	$31.27	$31.25	$31.30
Purchase #6	$165.59	4.699%	$173.3711	$173.37	$173.35	$173.40
Purchase #7	$215.35	8.466%	$233.5815	$233.58	$233.60	$233.60
7 purchase totals =	$625.47		$667.1100	$667.11	$667.05	$667.20