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	$211.76	8.346%	$229.4335	$229.43	$229.45	$229.40
Purchase #2	$176.89	5.287%	$186.2422	$186.24	$186.25	$186.20
Purchase #3	$43.47	5.545%	$45.8804	$45.88	$45.90	$45.90
Purchase #4	$102.70	10.767%	$113.7577	$113.76	$113.75	$113.80
Purchase #5	$29.89	4.663%	$31.2838	$31.28	$31.30	$31.30
Purchase #6	$30.75	13.820%	$34.9997	$35.00	$35.00	$35.00
Purchase #7	$241.39	5.827%	$255.4558	$255.46	$255.45	$255.50
7 purchase totals =	$836.85		$897.0531	$897.05	$897.10	$897.10