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	$250.36	10.368%	$276.3173	$276.32	$276.30	$276.30
Purchase #2	$108.66	3.527%	$112.4924	$112.49	$112.50	$112.50
Purchase #3	$38.88	6.341%	$41.3454	$41.35	$41.35	$41.30
Purchase #4	$246.90	4.688%	$258.4747	$258.47	$258.45	$258.50
Purchase #5	$107.44	3.820%	$111.5442	$111.54	$111.55	$111.50
Purchase #6	$207.54	9.495%	$227.2459	$227.25	$227.25	$227.20
Purchase #7	$196.55	5.857%	$208.0619	$208.06	$208.05	$208.10
7 purchase totals =	$1,156.33		$1,235.4818	$1,235.48	$1,235.45	$1,235.40