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	$231.46	10.335%	$255.3814	$255.38	$255.40	$255.40
Purchase #2	$101.88	13.811%	$115.9506	$115.95	$115.95	$116.00
Purchase #3	$29.50	7.205%	$31.6255	$31.63	$31.65	$31.60
Purchase #4	$11.41	6.185%	$12.1157	$12.12	$12.10	$12.10
Purchase #5	$92.30	8.645%	$100.2793	$100.28	$100.30	$100.30
Purchase #6	$75.32	3.636%	$78.0586	$78.06	$78.05	$78.10
Purchase #7	$224.84	3.652%	$233.0512	$233.05	$233.05	$233.10
7 purchase totals =	$766.71		$826.4623	$826.47	$826.50	$826.60