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	$178.88	6.562%	$190.6181	$190.62	$190.60	$190.60
Purchase #2	$110.63	11.495%	$123.3469	$123.35	$123.35	$123.30
Purchase #3	$112.85	3.786%	$117.1225	$117.12	$117.10	$117.10
Purchase #4	$92.67	9.405%	$101.3856	$101.39	$101.40	$101.40
Purchase #5	$114.60	11.578%	$127.8684	$127.87	$127.85	$127.90
Purchase #6	$198.61	6.700%	$211.9169	$211.92	$211.90	$211.90
Purchase #7	$175.79	5.698%	$185.8065	$185.81	$185.80	$185.80
7 purchase totals =	$984.03		$1,058.0649	$1,058.08	$1,058.00	$1,058.00