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	$68.32	4.820%	$71.613	$71.61	$71.60	$71.60
Purchase #2	$68.56	3.606%	$71.0323	$71.03	$71.05	$71.00
Purchase #3	$165.50	7.665%	$178.1856	$178.19	$178.20	$178.20
Purchase #4	$88.51	13.867%	$100.7837	$100.78	$100.80	$100.80
Purchase #5	$22.91	8.489%	$24.8548	$24.85	$24.85	$24.90
Purchase #6	$240.93	10.395%	$265.9747	$265.97	$265.95	$266.00
Purchase #7	$89.40	4.599%	$93.5115	$93.51	$93.50	$93.50
7 purchase totals =	$744.13		$805.9556	$805.94	$805.95	$806.00