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	$167.97	10.380%	$185.4053	$185.41	$185.40	$185.40
Purchase #2	$156.25	6.111%	$165.7984	$165.80	$165.80	$165.80
Purchase #3	$120.37	11.782%	$134.552	$134.55	$134.55	$134.60
Purchase #4	$198.72	8.653%	$215.9152	$215.92	$215.90	$215.90
Purchase #5	$66.79	12.495%	$75.1354	$75.14	$75.15	$75.10
Purchase #6	$114.42	12.342%	$128.5417	$128.54	$128.55	$128.50
Purchase #7	$38.73	9.410%	$42.3745	$42.37	$42.35	$42.40
7 purchase totals =	$863.25		$947.7225	$947.73	$947.70	$947.70