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	$167.84	11.499%	$187.1399	$187.14	$187.15	$187.10
Purchase #2	$40.60	5.667%	$42.9008	$42.90	$42.90	$42.90
Purchase #3	$187.54	6.563%	$199.8483	$199.85	$199.85	$199.80
Purchase #4	$193.56	5.242%	$203.7064	$203.71	$203.70	$203.70
Purchase #5	$116.27	3.581%	$120.4336	$120.43	$120.45	$120.40
Purchase #6	$12.35	4.850%	$12.949	$12.95	$12.95	$12.90
Purchase #7	$169.72	11.587%	$189.3855	$189.39	$189.40	$189.40
7 purchase totals =	$887.88		$956.3635	$956.37	$956.40	$956.20