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	$246.70	10.540%	$272.7022	$272.70	$272.70	$272.70
Purchase #2	$146.43	13.742%	$166.5524	$166.55	$166.55	$166.60
Purchase #3	$151.82	13.560%	$172.4068	$172.41	$172.40	$172.40
Purchase #4	$124.74	7.153%	$133.6627	$133.66	$133.65	$133.70
Purchase #5	$99.59	9.682%	$109.2323	$109.23	$109.25	$109.20
Purchase #6	$45.56	10.311%	$50.2577	$50.26	$50.25	$50.30
Purchase #7	$93.55	11.206%	$104.0332	$104.03	$104.05	$104.00
7 purchase totals =	$908.39		$1,008.8473	$1,008.84	$1,008.85	$1,008.90