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	$100.65	10.670%	$111.3894	$111.39	$111.40	$111.40
Purchase #2	$12.33	12.855%	$13.915	$13.92	$13.90	$13.90
Purchase #3	$171.26	6.796%	$182.8988	$182.90	$182.90	$182.90
Purchase #4	$169.71	12.290%	$190.5674	$190.57	$190.55	$190.60
Purchase #5	$49.74	7.420%	$53.4307	$53.43	$53.45	$53.40
Purchase #6	$82.78	3.723%	$85.8619	$85.86	$85.85	$85.90
Purchase #7	$128.27	7.588%	$138.0031	$138.00	$138.00	$138.00
7 purchase totals =	$714.74		$776.0663	$776.07	$776.05	$776.10