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	$212.54	5.551%	$224.3381	$224.34	$224.35	$224.30
Purchase #2	$59.66	4.637%	$62.4264	$62.43	$62.45	$62.40
Purchase #3	$46.55	5.131%	$48.9385	$48.94	$48.95	$48.90
Purchase #4	$40.43	5.676%	$42.7248	$42.72	$42.70	$42.70
Purchase #5	$122.72	3.496%	$127.0103	$127.01	$127.00	$127.00
Purchase #6	$58.44	8.636%	$63.4869	$63.49	$63.50	$63.50
Purchase #7	$243.56	8.742%	$264.852	$264.85	$264.85	$264.90
7 purchase totals =	$783.90		$833.7770	$833.78	$833.80	$833.70