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	$83.46	6.805%	$89.1395	$89.14	$89.15	$89.10
Purchase #2	$151.96	5.370%	$160.1203	$160.12	$160.10	$160.10
Purchase #3	$117.59	4.610%	$123.0109	$123.01	$123.00	$123.00
Purchase #4	$29.46	8.805%	$32.054	$32.05	$32.05	$32.10
Purchase #5	$233.84	12.153%	$262.2586	$262.26	$262.25	$262.30
Purchase #6	$38.77	7.820%	$41.8018	$41.80	$41.80	$41.80
Purchase #7	$43.40	9.785%	$47.6467	$47.65	$47.65	$47.60
7 purchase totals =	$698.48		$756.0318	$756.03	$756.00	$756.00