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	$99.93	11.831%	$111.7527	$111.75	$111.75	$111.80
Purchase #2	$185.60	4.764%	$194.442	$194.44	$194.45	$194.40
Purchase #3	$205.76	9.566%	$225.443	$225.44	$225.45	$225.40
Purchase #4	$243.55	11.464%	$271.4706	$271.47	$271.45	$271.50
Purchase #5	$47.79	3.506%	$49.4655	$49.47	$49.45	$49.50
Purchase #6	$140.47	13.869%	$159.9518	$159.95	$159.95	$160.00
Purchase #7	$55.64	10.139%	$61.2813	$61.28	$61.30	$61.30
7 purchase totals =	$978.74		$1,073.8069	$1,073.80	$1,073.80	$1,073.90