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	$9.38	8.359%	$10.1641	$10.16	$10.15	$10.20
Purchase #2	$155.29	8.817%	$168.9819	$168.98	$169.00	$169.00
Purchase #3	$140.49	10.206%	$154.8284	$154.83	$154.85	$154.80
Purchase #4	$44.25	9.148%	$48.298	$48.30	$48.30	$48.30
Purchase #5	$179.81	11.568%	$200.6104	$200.61	$200.60	$200.60
Purchase #6	$116.89	9.316%	$127.7795	$127.78	$127.80	$127.80
Purchase #7	$68.45	12.860%	$77.2527	$77.25	$77.25	$77.30
7 purchase totals =	$714.56		$787.9150	$787.91	$787.95	$788.00