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	$194.95	10.513%	$215.4451	$215.45	$215.45	$215.40
Purchase #2	$127.88	11.233%	$142.2448	$142.24	$142.25	$142.20
Purchase #3	$42.94	4.757%	$44.9827	$44.98	$45.00	$45.00
Purchase #4	$147.35	7.305%	$158.1139	$158.11	$158.10	$158.10
Purchase #5	$9.95	6.773%	$10.6239	$10.62	$10.60	$10.60
Purchase #6	$72.29	8.376%	$78.345	$78.35	$78.35	$78.30
Purchase #7	$45.63	4.735%	$47.7906	$47.79	$47.80	$47.80
7 purchase totals =	$640.99		$697.5460	$697.54	$697.55	$697.40