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	$17.43	9.226%	$19.0381	$19.04	$19.05	$19.00
Purchase #2	$58.81	5.534%	$62.0645	$62.06	$62.05	$62.10
Purchase #3	$80.72	10.825%	$89.4579	$89.46	$89.45	$89.50
Purchase #4	$58.45	9.826%	$64.1933	$64.19	$64.20	$64.20
Purchase #5	$127.67	11.711%	$142.6214	$142.62	$142.60	$142.60
Purchase #6	$127.97	6.121%	$135.803	$135.80	$135.80	$135.80
Purchase #7	$24.98	10.168%	$27.52	$27.52	$27.50	$27.50
7 purchase totals =	$496.03		$540.6982	$540.69	$540.65	$540.70