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	$178.81	12.200%	$200.6248	$200.62	$200.60	$200.60
Purchase #2	$155.77	10.674%	$172.3969	$172.40	$172.40	$172.40
Purchase #3	$22.79	4.572%	$23.832	$23.83	$23.85	$23.80
Purchase #4	$125.89	10.498%	$139.1059	$139.11	$139.10	$139.10
Purchase #5	$69.34	12.296%	$77.866	$77.87	$77.85	$77.90
Purchase #6	$189.87	3.625%	$196.7528	$196.75	$196.75	$196.80
Purchase #7	$232.84	9.161%	$254.1705	$254.17	$254.15	$254.20
7 purchase totals =	$975.31		$1,064.7489	$1,064.75	$1,064.70	$1,064.80