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	$180.31	4.319%	$188.0976	$188.10	$188.10	$188.10
Purchase #2	$105.32	6.748%	$112.427	$112.43	$112.45	$112.40
Purchase #3	$157.62	9.448%	$172.5119	$172.51	$172.50	$172.50
Purchase #4	$62.63	3.142%	$64.5978	$64.60	$64.60	$64.60
Purchase #5	$46.73	9.874%	$51.3441	$51.34	$51.35	$51.30
Purchase #6	$244.44	13.474%	$277.3758	$277.38	$277.40	$277.40
Purchase #7	$76.77	7.176%	$82.279	$82.28	$82.30	$82.30
7 purchase totals =	$873.82		$948.6332	$948.64	$948.70	$948.60