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	$128.28	13.346%	$145.4002	$145.40	$145.40	$145.40
Purchase #2	$96.99	6.508%	$103.3021	$103.30	$103.30	$103.30
Purchase #3	$42.58	5.133%	$44.7656	$44.77	$44.75	$44.80
Purchase #4	$42.78	6.496%	$45.559	$45.56	$45.55	$45.60
Purchase #5	$117.76	8.438%	$127.6966	$127.70	$127.70	$127.70
Purchase #6	$78.60	6.670%	$83.8426	$83.84	$83.85	$83.80
Purchase #7	$167.66	11.274%	$186.562	$186.56	$186.55	$186.60
7 purchase totals =	$674.65		$737.1281	$737.13	$737.10	$737.20