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	$115.28	10.711%	$127.6276	$127.63	$127.65	$127.60
Purchase #2	$92.42	6.224%	$98.1722	$98.17	$98.15	$98.20
Purchase #3	$102.25	7.212%	$109.6243	$109.62	$109.60	$109.60
Purchase #4	$93.72	5.180%	$98.5747	$98.57	$98.55	$98.60
Purchase #5	$12.64	7.169%	$13.5462	$13.55	$13.55	$13.50
Purchase #6	$147.85	11.446%	$164.7729	$164.77	$164.75	$164.80
Purchase #7	$169.52	12.717%	$191.0779	$191.08	$191.10	$191.10
7 purchase totals =	$733.68		$803.3958	$803.39	$803.35	$803.40