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	$28.91	9.652%	$31.7004	$31.70	$31.70	$31.70
Purchase #2	$167.50	3.797%	$173.86	$173.86	$173.85	$173.90
Purchase #3	$15.28	4.162%	$15.916	$15.92	$15.90	$15.90
Purchase #4	$95.79	4.731%	$100.3218	$100.32	$100.30	$100.30
Purchase #5	$134.49	8.523%	$145.9526	$145.95	$145.95	$146.00
Purchase #6	$201.82	5.353%	$212.6234	$212.62	$212.60	$212.60
Purchase #7	$184.72	6.144%	$196.0692	$196.07	$196.05	$196.10
7 purchase totals =	$828.51		$876.4434	$876.44	$876.35	$876.50