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	$230.55	6.641%	$245.8608	$245.86	$245.85	$245.90
Purchase #2	$145.73	12.694%	$164.229	$164.23	$164.25	$164.20
Purchase #3	$40.78	11.774%	$45.5814	$45.58	$45.60	$45.60
Purchase #4	$116.78	7.179%	$125.1636	$125.16	$125.15	$125.20
Purchase #5	$81.42	4.530%	$85.1083	$85.11	$85.10	$85.10
Purchase #6	$230.58	10.462%	$254.7033	$254.70	$254.70	$254.70
Purchase #7	$145.60	6.367%	$154.8704	$154.87	$154.85	$154.90
7 purchase totals =	$991.44		$1,075.5168	$1,075.51	$1,075.50	$1,075.60