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	$131.47	11.635%	$146.7665	$146.77	$146.75	$146.80
Purchase #2	$205.80	11.770%	$230.0227	$230.02	$230.00	$230.00
Purchase #3	$22.33	11.285%	$24.8499	$24.85	$24.85	$24.80
Purchase #4	$157.77	5.168%	$165.9236	$165.92	$165.90	$165.90
Purchase #5	$17.90	5.527%	$18.8893	$18.89	$18.90	$18.90
Purchase #6	$95.98	6.353%	$102.0776	$102.08	$102.10	$102.10
Purchase #7	$91.46	9.476%	$100.1267	$100.13	$100.15	$100.10
7 purchase totals =	$722.71		$788.6563	$788.66	$788.65	$788.60