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	$168.50	4.267%	$175.6899	$175.69	$175.70	$175.70
Purchase #2	$130.86	9.319%	$143.0548	$143.05	$143.05	$143.10
Purchase #3	$165.87	3.848%	$172.2527	$172.25	$172.25	$172.30
Purchase #4	$187.86	5.504%	$198.1998	$198.20	$198.20	$198.20
Purchase #5	$174.76	12.641%	$196.8514	$196.85	$196.85	$196.90
Purchase #6	$178.92	7.349%	$192.0688	$192.07	$192.05	$192.10
Purchase #7	$123.75	6.771%	$132.1291	$132.13	$132.15	$132.10
7 purchase totals =	$1,130.52		$1,210.2465	$1,210.24	$1,210.25	$1,210.40