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	$195.27	7.346%	$209.6145	$209.61	$209.60	$209.60
Purchase #2	$100.46	11.773%	$112.2872	$112.29	$112.30	$112.30
Purchase #3	$152.64	8.730%	$165.9655	$165.97	$165.95	$166.00
Purchase #4	$75.59	4.332%	$78.8646	$78.86	$78.85	$78.90
Purchase #5	$15.95	13.151%	$18.0476	$18.05	$18.05	$18.00
Purchase #6	$63.72	6.456%	$67.8338	$67.83	$67.85	$67.80
Purchase #7	$241.36	4.563%	$252.3733	$252.37	$252.35	$252.40
7 purchase totals =	$844.99		$904.9865	$904.98	$904.95	$905.00