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	$133.46	9.823%	$146.5698	$146.57	$146.55	$146.60
Purchase #2	$81.84	13.575%	$92.9498	$92.95	$92.95	$92.90
Purchase #3	$5.99	10.239%	$6.6033	$6.60	$6.60	$6.60
Purchase #4	$119.77	6.769%	$127.8772	$127.88	$127.90	$127.90
Purchase #5	$129.48	12.168%	$145.2351	$145.24	$145.25	$145.20
Purchase #6	$230.85	11.627%	$257.6909	$257.69	$257.70	$257.70
Purchase #7	$142.50	9.164%	$155.5587	$155.56	$155.55	$155.60
7 purchase totals =	$843.89		$932.4848	$932.49	$932.50	$932.50