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	$108.75	13.130%	$123.0289	$123.03	$123.05	$123.00
Purchase #2	$98.33	6.395%	$104.6182	$104.62	$104.60	$104.60
Purchase #3	$161.98	3.444%	$167.5586	$167.56	$167.55	$167.60
Purchase #4	$178.71	4.427%	$186.6215	$186.62	$186.60	$186.60
Purchase #5	$66.80	5.621%	$70.5548	$70.55	$70.55	$70.60
Purchase #6	$138.48	6.714%	$147.7775	$147.78	$147.80	$147.80
Purchase #7	$196.34	10.610%	$217.1717	$217.17	$217.15	$217.20
7 purchase totals =	$949.39		$1,017.3312	$1,017.33	$1,017.30	$1,017.40