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	$171.79	9.821%	$188.6615	$188.66	$188.65	$188.70
Purchase #2	$166.82	8.250%	$180.5827	$180.58	$180.60	$180.60
Purchase #3	$40.31	4.873%	$42.2743	$42.27	$42.25	$42.30
Purchase #4	$100.71	10.485%	$111.2694	$111.27	$111.25	$111.30
Purchase #5	$184.90	12.716%	$208.4119	$208.41	$208.40	$208.40
Purchase #6	$241.49	7.474%	$259.539	$259.54	$259.55	$259.50
Purchase #7	$85.44	10.455%	$94.3728	$94.37	$94.35	$94.40
7 purchase totals =	$991.46		$1,085.1116	$1,085.10	$1,085.05	$1,085.20