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	$94.58	10.606%	$104.6112	$104.61	$104.60	$104.60
Purchase #2	$158.85	12.233%	$178.2821	$178.28	$178.30	$178.30
Purchase #3	$81.75	13.335%	$92.6514	$92.65	$92.65	$92.70
Purchase #4	$172.66	6.339%	$183.6049	$183.60	$183.60	$183.60
Purchase #5	$232.78	9.133%	$254.0398	$254.04	$254.05	$254.00
Purchase #6	$239.59	10.464%	$264.6607	$264.66	$264.65	$264.70
Purchase #7	$100.95	4.109%	$105.098	$105.10	$105.10	$105.10
7 purchase totals =	$1,081.16		$1,182.9481	$1,182.94	$1,182.95	$1,183.00