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	$99.37	11.712%	$111.0082	$111.01	$111.00	$111.00
Purchase #2	$37.77	10.406%	$41.7003	$41.70	$41.70	$41.70
Purchase #3	$105.97	13.797%	$120.5907	$120.59	$120.60	$120.60
Purchase #4	$92.34	4.221%	$96.2377	$96.24	$96.25	$96.20
Purchase #5	$203.68	9.364%	$222.7526	$222.75	$222.75	$222.80
Purchase #6	$23.81	3.345%	$24.6064	$24.61	$24.60	$24.60
Purchase #7	$96.86	11.644%	$108.1384	$108.14	$108.15	$108.10
7 purchase totals =	$659.80		$725.0343	$725.04	$725.05	$725.00