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	$224.62	11.679%	$250.8534	$250.85	$250.85	$250.90
Purchase #2	$72.25	12.562%	$81.326	$81.33	$81.35	$81.30
Purchase #3	$108.31	13.287%	$122.7011	$122.70	$122.70	$122.70
Purchase #4	$214.90	12.295%	$241.322	$241.32	$241.30	$241.30
Purchase #5	$121.45	5.336%	$127.9306	$127.93	$127.95	$127.90
Purchase #6	$176.53	6.393%	$187.8156	$187.82	$187.80	$187.80
Purchase #7	$175.33	7.767%	$188.9479	$188.95	$188.95	$188.90
7 purchase totals =	$1,093.39		$1,200.8966	$1,200.90	$1,200.90	$1,200.80