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	$237.91	10.842%	$263.7042	$263.70	$263.70	$263.70
Purchase #2	$222.46	4.162%	$231.7188	$231.72	$231.70	$231.70
Purchase #3	$109.82	10.727%	$121.6004	$121.60	$121.60	$121.60
Purchase #4	$155.34	11.370%	$173.0022	$173.00	$173.00	$173.00
Purchase #5	$49.78	12.480%	$55.9925	$55.99	$56.00	$56.00
Purchase #6	$56.29	5.790%	$59.5492	$59.55	$59.55	$59.50
Purchase #7	$147.88	5.274%	$155.6792	$155.68	$155.70	$155.70
7 purchase totals =	$979.48		$1,061.2465	$1,061.24	$1,061.25	$1,061.20