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	$247.56	8.783%	$269.3032	$269.30	$269.30	$269.30
Purchase #2	$153.36	3.301%	$158.4224	$158.42	$158.40	$158.40
Purchase #3	$221.60	10.760%	$245.4442	$245.44	$245.45	$245.40
Purchase #4	$237.64	13.434%	$269.5646	$269.56	$269.55	$269.60
Purchase #5	$24.52	3.444%	$25.3645	$25.36	$25.35	$25.40
Purchase #6	$70.39	11.450%	$78.4497	$78.45	$78.45	$78.40
Purchase #7	$93.48	3.626%	$96.8696	$96.87	$96.85	$96.90
7 purchase totals =	$1,048.55		$1,143.4182	$1,143.40	$1,143.35	$1,143.40