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	$206.83	8.826%	$225.0848	$225.08	$225.10	$225.10
Purchase #2	$100.29	13.487%	$113.8161	$113.82	$113.80	$113.80
Purchase #3	$101.47	12.640%	$114.2958	$114.30	$114.30	$114.30
Purchase #4	$110.67	11.233%	$123.1016	$123.10	$123.10	$123.10
Purchase #5	$209.37	7.370%	$224.8006	$224.80	$224.80	$224.80
Purchase #6	$117.58	8.566%	$127.6519	$127.65	$127.65	$127.70
Purchase #7	$152.41	10.719%	$168.7468	$168.75	$168.75	$168.70
7 purchase totals =	$998.62		$1,097.4976	$1,097.50	$1,097.50	$1,097.50