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	$157.42	6.693%	$167.9561	$167.96	$167.95	$168.00
Purchase #2	$185.65	12.397%	$208.665	$208.67	$208.65	$208.70
Purchase #3	$109.75	8.852%	$119.4651	$119.47	$119.45	$119.50
Purchase #4	$240.77	13.454%	$273.1632	$273.16	$273.15	$273.20
Purchase #5	$129.81	6.518%	$138.271	$138.27	$138.25	$138.30
Purchase #6	$91.60	9.356%	$100.1701	$100.17	$100.15	$100.20
Purchase #7	$141.29	12.123%	$158.4186	$158.42	$158.40	$158.40
7 purchase totals =	$1,056.29		$1,166.1091	$1,166.12	$1,166.00	$1,166.30