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	$69.47	13.509%	$78.8547	$78.85	$78.85	$78.90
Purchase #2	$59.67	4.735%	$62.4954	$62.50	$62.50	$62.50
Purchase #3	$27.95	4.847%	$29.3047	$29.30	$29.30	$29.30
Purchase #4	$30.67	12.817%	$34.601	$34.60	$34.60	$34.60
Purchase #5	$209.56	10.826%	$232.247	$232.25	$232.25	$232.20
Purchase #6	$90.95	11.308%	$101.2346	$101.23	$101.25	$101.20
Purchase #7	$53.76	10.608%	$59.4629	$59.46	$59.45	$59.50
7 purchase totals =	$542.03		$598.2003	$598.19	$598.20	$598.20