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	$158.88	8.399%	$172.2243	$172.22	$172.20	$172.20
Purchase #2	$70.71	12.120%	$79.2801	$79.28	$79.30	$79.30
Purchase #3	$173.79	3.661%	$180.1525	$180.15	$180.15	$180.20
Purchase #4	$201.78	6.854%	$215.61	$215.61	$215.60	$215.60
Purchase #5	$168.35	13.394%	$190.8988	$190.90	$190.90	$190.90
Purchase #6	$181.32	10.570%	$200.4855	$200.49	$200.50	$200.50
Purchase #7	$113.49	12.318%	$127.4697	$127.47	$127.45	$127.50
7 purchase totals =	$1,068.32		$1,166.1209	$1,166.12	$1,166.10	$1,166.20