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	$188.75	8.795%	$205.3506	$205.35	$205.35	$205.40
Purchase #2	$46.98	5.578%	$49.6005	$49.60	$49.60	$49.60
Purchase #3	$66.49	8.752%	$72.3092	$72.31	$72.30	$72.30
Purchase #4	$80.37	13.196%	$90.9756	$90.98	$91.00	$91.00
Purchase #5	$49.49	6.730%	$52.8207	$52.82	$52.80	$52.80
Purchase #6	$130.61	4.692%	$136.7382	$136.74	$136.75	$136.70
Purchase #7	$109.90	6.279%	$116.8006	$116.80	$116.80	$116.80
7 purchase totals =	$672.59		$724.5954	$724.60	$724.60	$724.60