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	$108.72	13.572%	$123.4755	$123.48	$123.50	$123.50
Purchase #2	$45.87	13.588%	$52.1028	$52.10	$52.10	$52.10
Purchase #3	$249.80	3.289%	$258.0159	$258.02	$258.00	$258.00
Purchase #4	$11.91	6.818%	$12.722	$12.72	$12.70	$12.70
Purchase #5	$242.44	8.245%	$262.4292	$262.43	$262.45	$262.40
Purchase #6	$143.95	6.486%	$153.2866	$153.29	$153.30	$153.30
Purchase #7	$148.81	10.494%	$164.4261	$164.43	$164.45	$164.40
7 purchase totals =	$951.50		$1,026.4581	$1,026.47	$1,026.50	$1,026.40