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	$94.84	5.300%	$99.8665	$99.87	$99.85	$99.90
Purchase #2	$114.71	11.144%	$127.4933	$127.49	$127.50	$127.50
Purchase #3	$185.63	10.783%	$205.6465	$205.65	$205.65	$205.60
Purchase #4	$63.93	4.818%	$67.0101	$67.01	$67.00	$67.00
Purchase #5	$141.41	8.254%	$153.082	$153.08	$153.10	$153.10
Purchase #6	$230.61	8.465%	$250.1311	$250.13	$250.15	$250.10
Purchase #7	$66.94	8.137%	$72.3869	$72.39	$72.40	$72.40
7 purchase totals =	$898.07		$975.6164	$975.62	$975.65	$975.60