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	$40.64	11.289%	$45.2278	$45.23	$45.25	$45.20
Purchase #2	$160.60	3.607%	$166.3928	$166.39	$166.40	$166.40
Purchase #3	$189.58	12.525%	$213.3249	$213.32	$213.30	$213.30
Purchase #4	$112.69	4.662%	$117.9436	$117.94	$117.95	$117.90
Purchase #5	$40.45	12.309%	$45.429	$45.43	$45.45	$45.40
Purchase #6	$108.47	13.735%	$123.3684	$123.37	$123.35	$123.40
Purchase #7	$110.35	11.158%	$122.6629	$122.66	$122.65	$122.70
7 purchase totals =	$762.78		$834.3494	$834.34	$834.35	$834.30