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	$181.96	13.118%	$205.8295	$205.83	$205.85	$205.80
Purchase #2	$104.69	7.488%	$112.5292	$112.53	$112.55	$112.50
Purchase #3	$55.30	4.749%	$57.9262	$57.93	$57.95	$57.90
Purchase #4	$29.41	13.622%	$33.4162	$33.42	$33.40	$33.40
Purchase #5	$213.32	7.675%	$229.6923	$229.69	$229.70	$229.70
Purchase #6	$149.79	11.171%	$166.523	$166.52	$166.50	$166.50
Purchase #7	$170.76	3.445%	$176.6427	$176.64	$176.65	$176.60
7 purchase totals =	$905.23		$982.5591	$982.56	$982.60	$982.40