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	$67.43	7.371%	$72.4003	$72.40	$72.40	$72.40
Purchase #2	$93.97	8.173%	$101.6502	$101.65	$101.65	$101.70
Purchase #3	$214.32	4.332%	$223.6043	$223.60	$223.60	$223.60
Purchase #4	$219.36	7.308%	$235.3908	$235.39	$235.40	$235.40
Purchase #5	$173.52	13.343%	$196.6728	$196.67	$196.65	$196.70
Purchase #6	$112.39	7.248%	$120.536	$120.54	$120.55	$120.50
Purchase #7	$110.38	7.748%	$118.9322	$118.93	$118.95	$118.90
7 purchase totals =	$991.37		$1,069.1866	$1,069.18	$1,069.20	$1,069.20