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	$173.37	4.852%	$181.7819	$181.78	$181.80	$181.80
Purchase #2	$103.74	10.365%	$114.4927	$114.49	$114.50	$114.50
Purchase #3	$82.27	4.316%	$85.8208	$85.82	$85.80	$85.80
Purchase #4	$52.83	13.276%	$59.8437	$59.84	$59.85	$59.80
Purchase #5	$59.99	13.276%	$67.9543	$67.95	$67.95	$68.00
Purchase #6	$235.99	6.637%	$251.6527	$251.65	$251.65	$251.70
Purchase #7	$132.34	3.107%	$136.4518	$136.45	$136.45	$136.50
7 purchase totals =	$840.53		$897.9979	$897.98	$898.00	$898.10