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	$233.95	8.673%	$254.2405	$254.24	$254.25	$254.20
Purchase #2	$233.44	9.481%	$255.5724	$255.57	$255.55	$255.60
Purchase #3	$51.55	8.508%	$55.9359	$55.94	$55.95	$55.90
Purchase #4	$17.40	5.788%	$18.4071	$18.41	$18.40	$18.40
Purchase #5	$129.71	11.485%	$144.6072	$144.61	$144.60	$144.60
Purchase #6	$225.25	12.288%	$252.9287	$252.93	$252.95	$252.90
Purchase #7	$155.30	4.425%	$162.172	$162.17	$162.15	$162.20
7 purchase totals =	$1,046.60		$1,143.8638	$1,143.87	$1,143.85	$1,143.80