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	$60.43	8.822%	$65.7611	$65.76	$65.75	$65.80
Purchase #2	$11.57	11.120%	$12.8566	$12.86	$12.85	$12.90
Purchase #3	$126.62	8.318%	$137.1523	$137.15	$137.15	$137.20
Purchase #4	$150.62	4.176%	$156.9099	$156.91	$156.90	$156.90
Purchase #5	$113.87	8.871%	$123.9714	$123.97	$123.95	$124.00
Purchase #6	$100.45	6.116%	$106.5935	$106.59	$106.60	$106.60
Purchase #7	$91.96	9.769%	$100.9436	$100.94	$100.95	$100.90
7 purchase totals =	$655.52		$704.1884	$704.18	$704.15	$704.30