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	$13.71	5.476%	$14.4608	$14.46	$14.45	$14.50
Purchase #2	$182.99	3.784%	$189.9143	$189.91	$189.90	$189.90
Purchase #3	$80.57	13.685%	$91.596	$91.60	$91.60	$91.60
Purchase #4	$85.59	6.429%	$91.0926	$91.09	$91.10	$91.10
Purchase #5	$51.62	3.774%	$53.5681	$53.57	$53.55	$53.60
Purchase #6	$34.91	7.716%	$37.6037	$37.60	$37.60	$37.60
Purchase #7	$54.56	5.295%	$57.449	$57.45	$57.45	$57.40
7 purchase totals =	$503.95		$535.6845	$535.68	$535.65	$535.70