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	$27.42	5.146%	$28.831	$28.83	$28.85	$28.80
Purchase #2	$37.45	3.332%	$38.6978	$38.70	$38.70	$38.70
Purchase #3	$246.96	3.559%	$255.7493	$255.75	$255.75	$255.70
Purchase #4	$85.64	6.189%	$90.9403	$90.94	$90.95	$90.90
Purchase #5	$201.81	11.441%	$224.8991	$224.90	$224.90	$224.90
Purchase #6	$167.43	3.286%	$172.9317	$172.93	$172.95	$172.90
Purchase #7	$149.39	3.550%	$154.6933	$154.69	$154.70	$154.70
7 purchase totals =	$916.10		$966.7425	$966.74	$966.80	$966.60