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	$88.60	4.195%	$92.3168	$92.32	$92.30	$92.30
Purchase #2	$31.93	9.408%	$34.934	$34.93	$34.95	$34.90
Purchase #3	$156.69	11.855%	$175.2656	$175.27	$175.25	$175.30
Purchase #4	$67.83	10.346%	$74.8477	$74.85	$74.85	$74.80
Purchase #5	$38.34	11.543%	$42.7656	$42.77	$42.75	$42.80
Purchase #6	$189.47	4.773%	$198.5134	$198.51	$198.50	$198.50
Purchase #7	$143.70	8.460%	$155.857	$155.86	$155.85	$155.90
7 purchase totals =	$716.56		$774.5001	$774.51	$774.45	$774.50