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	$92.96	13.805%	$105.7931	$105.79	$105.80	$105.80
Purchase #2	$101.25	10.830%	$112.2154	$112.22	$112.20	$112.20
Purchase #3	$200.31	9.637%	$219.6139	$219.61	$219.60	$219.60
Purchase #4	$61.51	4.761%	$64.4385	$64.44	$64.45	$64.40
Purchase #5	$208.29	10.436%	$230.0271	$230.03	$230.05	$230.00
Purchase #6	$45.30	6.851%	$48.4035	$48.40	$48.40	$48.40
Purchase #7	$242.71	10.225%	$267.5271	$267.53	$267.55	$267.50
7 purchase totals =	$952.33		$1,048.0186	$1,048.02	$1,048.05	$1,047.90