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	$85.43	7.357%	$91.7151	$91.72	$91.70	$91.70
Purchase #2	$239.68	4.795%	$251.1727	$251.17	$251.15	$251.20
Purchase #3	$32.35	5.627%	$34.1703	$34.17	$34.15	$34.20
Purchase #4	$19.97	7.868%	$21.5412	$21.54	$21.55	$21.50
Purchase #5	$81.78	4.628%	$85.5648	$85.56	$85.55	$85.60
Purchase #6	$42.89	5.116%	$45.0843	$45.08	$45.10	$45.10
Purchase #7	$213.79	7.773%	$230.4079	$230.41	$230.40	$230.40
7 purchase totals =	$715.89		$759.6563	$759.65	$759.60	$759.70