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	$44.85	8.137%	$48.4994	$48.50	$48.50	$48.50
Purchase #2	$193.37	12.156%	$216.8761	$216.88	$216.90	$216.90
Purchase #3	$200.57	3.276%	$207.1407	$207.14	$207.15	$207.10
Purchase #4	$132.75	7.396%	$142.5682	$142.57	$142.55	$142.60
Purchase #5	$53.61	3.462%	$55.466	$55.47	$55.45	$55.50
Purchase #6	$229.34	7.400%	$246.3112	$246.31	$246.30	$246.30
Purchase #7	$90.53	6.682%	$96.5792	$96.58	$96.60	$96.60
7 purchase totals =	$945.02		$1,013.4408	$1,013.45	$1,013.45	$1,013.50