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	$111.70	4.192%	$116.3825	$116.38	$116.40	$116.40
Purchase #2	$158.64	4.341%	$165.5266	$165.53	$165.55	$165.50
Purchase #3	$112.36	7.810%	$121.1353	$121.14	$121.15	$121.10
Purchase #4	$147.94	3.596%	$153.2599	$153.26	$153.25	$153.30
Purchase #5	$65.30	13.151%	$73.8876	$73.89	$73.90	$73.90
Purchase #6	$77.52	13.557%	$88.0294	$88.03	$88.05	$88.00
Purchase #7	$53.52	10.789%	$59.2943	$59.29	$59.30	$59.30
7 purchase totals =	$726.98		$777.5156	$777.52	$777.60	$777.50