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	$228.25	11.745%	$255.058	$255.06	$255.05	$255.10
Purchase #2	$184.99	11.572%	$206.397	$206.40	$206.40	$206.40
Purchase #3	$24.91	12.721%	$28.0788	$28.08	$28.10	$28.10
Purchase #4	$32.65	6.650%	$34.8212	$34.82	$34.80	$34.80
Purchase #5	$180.88	8.801%	$196.7992	$196.80	$196.80	$196.80
Purchase #6	$112.78	13.176%	$127.6399	$127.64	$127.65	$127.60
Purchase #7	$169.71	11.203%	$188.7226	$188.72	$188.70	$188.70
7 purchase totals =	$934.17		$1,037.5167	$1,037.52	$1,037.50	$1,037.50