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	$155.79	5.808%	$164.8383	$164.84	$164.85	$164.80
Purchase #2	$153.63	13.162%	$173.8508	$173.85	$173.85	$173.90
Purchase #3	$59.73	13.258%	$67.649	$67.65	$67.65	$67.60
Purchase #4	$61.92	6.741%	$66.094	$66.09	$66.10	$66.10
Purchase #5	$72.70	11.157%	$80.8111	$80.81	$80.80	$80.80
Purchase #6	$206.89	6.849%	$221.0599	$221.06	$221.05	$221.10
Purchase #7	$127.56	11.264%	$141.9284	$141.93	$141.95	$141.90
7 purchase totals =	$838.22		$916.2315	$916.23	$916.25	$916.20