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	$215.78	5.251%	$227.1106	$227.11	$227.10	$227.10
Purchase #2	$171.69	9.856%	$188.6118	$188.61	$188.60	$188.60
Purchase #3	$187.26	8.123%	$202.4711	$202.47	$202.45	$202.50
Purchase #4	$32.75	13.395%	$37.1369	$37.14	$37.15	$37.10
Purchase #5	$66.44	5.754%	$70.263	$70.26	$70.25	$70.30
Purchase #6	$130.40	11.646%	$145.5864	$145.59	$145.60	$145.60
Purchase #7	$151.90	5.321%	$159.9826	$159.98	$160.00	$160.00
7 purchase totals =	$956.22		$1,031.1624	$1,031.16	$1,031.15	$1,031.20