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	$191.46	10.360%	$211.2953	$211.30	$211.30	$211.30
Purchase #2	$127.84	9.342%	$139.7828	$139.78	$139.80	$139.80
Purchase #3	$159.87	4.768%	$167.4926	$167.49	$167.50	$167.50
Purchase #4	$125.59	13.553%	$142.6112	$142.61	$142.60	$142.60
Purchase #5	$133.26	9.615%	$146.0729	$146.07	$146.05	$146.10
Purchase #6	$171.31	11.228%	$190.5447	$190.54	$190.55	$190.50
Purchase #7	$215.36	4.622%	$225.3139	$225.31	$225.30	$225.30
7 purchase totals =	$1,124.69		$1,223.1134	$1,223.10	$1,223.10	$1,223.10