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	$105.31	12.677%	$118.6601	$118.66	$118.65	$118.70
Purchase #2	$14.76	10.860%	$16.3629	$16.36	$16.35	$16.40
Purchase #3	$81.64	11.302%	$90.867	$90.87	$90.85	$90.90
Purchase #4	$111.63	3.321%	$115.3372	$115.34	$115.35	$115.30
Purchase #5	$40.71	12.131%	$45.6485	$45.65	$45.65	$45.60
Purchase #6	$49.66	10.192%	$54.7213	$54.72	$54.70	$54.70
Purchase #7	$209.74	11.455%	$233.7657	$233.77	$233.75	$233.80
7 purchase totals =	$613.45		$675.3627	$675.37	$675.30	$675.40