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	$155.80	9.813%	$171.0887	$171.09	$171.10	$171.10
Purchase #2	$203.93	13.531%	$231.5238	$231.52	$231.50	$231.50
Purchase #3	$183.83	11.704%	$205.3455	$205.35	$205.35	$205.30
Purchase #4	$131.40	11.475%	$146.4782	$146.48	$146.50	$146.50
Purchase #5	$124.31	10.640%	$137.5366	$137.54	$137.55	$137.50
Purchase #6	$99.39	7.711%	$107.054	$107.05	$107.05	$107.10
Purchase #7	$244.46	5.245%	$257.2819	$257.28	$257.30	$257.30
7 purchase totals =	$1,143.12		$1,256.3087	$1,256.31	$1,256.35	$1,256.30