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	$177.46	10.667%	$196.3897	$196.39	$196.40	$196.40
Purchase #2	$94.53	9.466%	$103.4782	$103.48	$103.50	$103.50
Purchase #3	$39.66	10.735%	$43.9175	$43.92	$43.90	$43.90
Purchase #4	$137.43	7.176%	$147.292	$147.29	$147.30	$147.30
Purchase #5	$138.65	5.327%	$146.0359	$146.04	$146.05	$146.00
Purchase #6	$44.48	10.333%	$49.0761	$49.08	$49.10	$49.10
Purchase #7	$39.55	8.808%	$43.0336	$43.03	$43.05	$43.00
7 purchase totals =	$671.76		$729.2230	$729.23	$729.30	$729.20