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	$56.80	5.293%	$59.8064	$59.81	$59.80	$59.80
Purchase #2	$26.74	9.742%	$29.345	$29.35	$29.35	$29.30
Purchase #3	$200.28	11.146%	$222.6032	$222.60	$222.60	$222.60
Purchase #4	$97.41	5.114%	$102.3915	$102.39	$102.40	$102.40
Purchase #5	$207.61	4.773%	$217.5192	$217.52	$217.50	$217.50
Purchase #6	$236.63	7.823%	$255.1416	$255.14	$255.15	$255.10
Purchase #7	$30.98	13.529%	$35.1713	$35.17	$35.15	$35.20
7 purchase totals =	$856.45		$921.9782	$921.98	$921.95	$921.90