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	$232.58	9.811%	$255.3984	$255.40	$255.40	$255.40
Purchase #2	$178.34	12.694%	$200.9785	$200.98	$201.00	$201.00
Purchase #3	$194.65	7.606%	$209.4551	$209.46	$209.45	$209.50
Purchase #4	$52.28	13.840%	$59.5156	$59.52	$59.50	$59.50
Purchase #5	$220.94	4.394%	$230.6481	$230.65	$230.65	$230.60
Purchase #6	$39.49	4.168%	$41.1359	$41.14	$41.15	$41.10
Purchase #7	$71.46	9.486%	$78.2387	$78.24	$78.25	$78.20
7 purchase totals =	$989.74		$1,075.3703	$1,075.39	$1,075.40	$1,075.30