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	$59.55	13.529%	$67.6065	$67.61	$67.60	$67.60
Purchase #2	$92.77	11.138%	$103.1027	$103.10	$103.10	$103.10
Purchase #3	$30.59	6.588%	$32.6053	$32.61	$32.60	$32.60
Purchase #4	$136.81	10.274%	$150.8659	$150.87	$150.85	$150.90
Purchase #5	$164.37	12.175%	$184.382	$184.38	$184.40	$184.40
Purchase #6	$14.76	6.705%	$15.7497	$15.75	$15.75	$15.70
Purchase #7	$20.97	12.172%	$23.5225	$23.52	$23.50	$23.50
7 purchase totals =	$519.82		$577.8346	$577.84	$577.80	$577.80