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	$97.48	8.507%	$105.7726	$105.77	$105.75	$105.80
Purchase #2	$12.39	3.246%	$12.7922	$12.79	$12.80	$12.80
Purchase #3	$168.95	13.246%	$191.3291	$191.33	$191.35	$191.30
Purchase #4	$35.37	7.527%	$38.0323	$38.03	$38.05	$38.00
Purchase #5	$48.80	4.490%	$50.9911	$50.99	$51.00	$51.00
Purchase #6	$39.48	13.624%	$44.8588	$44.86	$44.85	$44.90
Purchase #7	$70.35	11.137%	$78.1849	$78.18	$78.20	$78.20
7 purchase totals =	$472.82		$521.9610	$521.95	$522.00	$522.00