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	$236.39	13.832%	$269.0875	$269.09	$269.10	$269.10
Purchase #2	$119.99	9.305%	$131.1551	$131.16	$131.15	$131.20
Purchase #3	$201.56	5.126%	$211.892	$211.89	$211.90	$211.90
Purchase #4	$134.45	5.471%	$141.8058	$141.81	$141.80	$141.80
Purchase #5	$57.78	13.823%	$65.7669	$65.77	$65.75	$65.80
Purchase #6	$131.64	8.734%	$143.1374	$143.14	$143.15	$143.10
Purchase #7	$191.60	8.847%	$208.5509	$208.55	$208.55	$208.60
7 purchase totals =	$1,073.41		$1,171.3956	$1,171.41	$1,171.40	$1,171.50