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	$13.86	7.867%	$14.9504	$14.95	$14.95	$15.00
Purchase #2	$24.38	5.163%	$25.6387	$25.64	$25.65	$25.60
Purchase #3	$133.48	11.522%	$148.8596	$148.86	$148.85	$148.90
Purchase #4	$52.82	11.217%	$58.7448	$58.74	$58.75	$58.70
Purchase #5	$34.88	8.760%	$37.9355	$37.94	$37.95	$37.90
Purchase #6	$116.80	5.678%	$123.4319	$123.43	$123.45	$123.40
Purchase #7	$42.56	11.471%	$47.4421	$47.44	$47.45	$47.40
7 purchase totals =	$418.78		$457.0030	$457.00	$457.05	$456.90