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	$68.35	5.452%	$72.0764	$72.08	$72.10	$72.10
Purchase #2	$243.50	11.476%	$271.4441	$271.44	$271.45	$271.40
Purchase #3	$128.69	4.152%	$134.0332	$134.03	$134.05	$134.00
Purchase #4	$141.34	12.534%	$159.0556	$159.06	$159.05	$159.10
Purchase #5	$238.74	5.799%	$252.5845	$252.58	$252.60	$252.60
Purchase #6	$81.78	10.512%	$90.3767	$90.38	$90.40	$90.40
Purchase #7	$84.91	7.722%	$91.4668	$91.47	$91.45	$91.50
7 purchase totals =	$987.31		$1,071.0373	$1,071.04	$1,071.10	$1,071.10