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	$95.84	10.367%	$105.7757	$105.78	$105.80	$105.80
Purchase #2	$105.61	5.553%	$111.4745	$111.47	$111.45	$111.50
Purchase #3	$118.77	7.584%	$127.7775	$127.78	$127.80	$127.80
Purchase #4	$225.33	9.156%	$245.9612	$245.96	$245.95	$246.00
Purchase #5	$241.43	11.803%	$269.926	$269.93	$269.95	$269.90
Purchase #6	$194.80	6.857%	$208.1574	$208.16	$208.15	$208.20
Purchase #7	$184.82	8.640%	$200.7884	$200.79	$200.80	$200.80
7 purchase totals =	$1,166.60		$1,269.8607	$1,269.87	$1,269.90	$1,270.00