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	$157.76	6.798%	$168.4845	$168.48	$168.50	$168.50
Purchase #2	$7.41	13.470%	$8.4081	$8.41	$8.40	$8.40
Purchase #3	$54.44	13.724%	$61.9113	$61.91	$61.90	$61.90
Purchase #4	$247.42	4.393%	$258.2892	$258.29	$258.30	$258.30
Purchase #5	$108.96	4.126%	$113.4557	$113.46	$113.45	$113.50
Purchase #6	$138.79	5.549%	$146.4915	$146.49	$146.50	$146.50
Purchase #7	$226.77	7.769%	$244.3878	$244.39	$244.40	$244.40
7 purchase totals =	$941.55		$1,001.4281	$1,001.43	$1,001.45	$1,001.50