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	$25.34	4.177%	$26.3985	$26.40	$26.40	$26.40
Purchase #2	$207.77	13.667%	$236.1659	$236.17	$236.15	$236.20
Purchase #3	$123.47	10.480%	$136.4097	$136.41	$136.40	$136.40
Purchase #4	$188.43	4.469%	$196.8509	$196.85	$196.85	$196.90
Purchase #5	$106.83	10.543%	$118.0931	$118.09	$118.10	$118.10
Purchase #6	$204.92	12.663%	$230.869	$230.87	$230.85	$230.90
Purchase #7	$126.35	11.789%	$141.2454	$141.25	$141.25	$141.20
7 purchase totals =	$983.11		$1,086.0325	$1,086.04	$1,086.00	$1,086.10