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	$130.54	13.270%	$147.8627	$147.86	$147.85	$147.90
Purchase #2	$161.27	7.863%	$173.9507	$173.95	$173.95	$174.00
Purchase #3	$68.36	6.592%	$72.8663	$72.87	$72.85	$72.90
Purchase #4	$5.45	4.872%	$5.7155	$5.72	$5.70	$5.70
Purchase #5	$27.71	12.123%	$31.0693	$31.07	$31.05	$31.10
Purchase #6	$100.82	10.293%	$111.1974	$111.20	$111.20	$111.20
Purchase #7	$155.92	8.660%	$169.4227	$169.42	$169.40	$169.40
7 purchase totals =	$650.07		$712.0846	$712.09	$712.00	$712.20