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	$124.50	9.723%	$136.6051	$136.61	$136.60	$136.60
Purchase #2	$240.70	8.255%	$260.5698	$260.57	$260.55	$260.60
Purchase #3	$128.73	3.139%	$132.7708	$132.77	$132.75	$132.80
Purchase #4	$181.73	11.791%	$203.1578	$203.16	$203.15	$203.20
Purchase #5	$72.47	10.568%	$80.1286	$80.13	$80.15	$80.10
Purchase #6	$94.46	11.209%	$105.048	$105.05	$105.05	$105.00
Purchase #7	$158.43	5.759%	$167.554	$167.55	$167.55	$167.60
7 purchase totals =	$1,001.02		$1,085.8341	$1,085.84	$1,085.80	$1,085.90