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	$44.70	4.820%	$46.8545	$46.85	$46.85	$46.90
Purchase #2	$198.86	11.443%	$221.6155	$221.62	$221.60	$221.60
Purchase #3	$111.75	10.299%	$123.2591	$123.26	$123.25	$123.30
Purchase #4	$247.70	4.138%	$257.9498	$257.95	$257.95	$257.90
Purchase #5	$20.38	3.122%	$21.0163	$21.02	$21.00	$21.00
Purchase #6	$213.37	4.182%	$222.2931	$222.29	$222.30	$222.30
Purchase #7	$182.61	9.596%	$200.1333	$200.13	$200.15	$200.10
7 purchase totals =	$1,019.37		$1,093.1216	$1,093.12	$1,093.10	$1,093.10