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	$213.31	13.864%	$242.8833	$242.88	$242.90	$242.90
Purchase #2	$11.82	5.571%	$12.4785	$12.48	$12.50	$12.50
Purchase #3	$19.82	4.608%	$20.7333	$20.73	$20.75	$20.70
Purchase #4	$111.89	11.245%	$124.472	$124.47	$124.45	$124.50
Purchase #5	$64.56	3.772%	$66.9952	$67.00	$67.00	$67.00
Purchase #6	$241.60	11.251%	$268.7824	$268.78	$268.80	$268.80
Purchase #7	$62.83	10.795%	$69.6125	$69.61	$69.60	$69.60
7 purchase totals =	$725.83		$805.9572	$805.95	$806.00	$806.00