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	$248.55	6.193%	$263.9427	$263.94	$263.95	$263.90
Purchase #2	$85.96	7.481%	$92.3907	$92.39	$92.40	$92.40
Purchase #3	$57.48	3.140%	$59.2849	$59.28	$59.30	$59.30
Purchase #4	$127.83	13.191%	$144.6921	$144.69	$144.70	$144.70
Purchase #5	$84.64	8.794%	$92.0832	$92.08	$92.10	$92.10
Purchase #6	$224.45	7.816%	$241.993	$241.99	$242.00	$242.00
Purchase #7	$174.92	3.572%	$181.1681	$181.17	$181.15	$181.20
7 purchase totals =	$1,003.83		$1,075.5547	$1,075.54	$1,075.60	$1,075.60