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	$107.90	3.653%	$111.8416	$111.84	$111.85	$111.80
Purchase #2	$161.88	10.670%	$179.1526	$179.15	$179.15	$179.20
Purchase #3	$196.30	9.510%	$214.9681	$214.97	$214.95	$215.00
Purchase #4	$236.74	5.756%	$250.3668	$250.37	$250.35	$250.40
Purchase #5	$160.53	6.699%	$171.2839	$171.28	$171.30	$171.30
Purchase #6	$194.38	7.153%	$208.284	$208.28	$208.30	$208.30
Purchase #7	$175.99	13.313%	$199.4195	$199.42	$199.40	$199.40
7 purchase totals =	$1,233.72		$1,335.3165	$1,335.31	$1,335.30	$1,335.40