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	$240.80	8.174%	$260.483	$260.48	$260.50	$260.50
Purchase #2	$158.45	11.346%	$176.4277	$176.43	$176.45	$176.40
Purchase #3	$54.72	8.653%	$59.4549	$59.45	$59.45	$59.50
Purchase #4	$33.43	8.737%	$36.3508	$36.35	$36.35	$36.40
Purchase #5	$204.60	5.227%	$215.2944	$215.29	$215.30	$215.30
Purchase #6	$51.52	11.618%	$57.5056	$57.51	$57.50	$57.50
Purchase #7	$210.73	7.549%	$226.638	$226.64	$226.65	$226.60
7 purchase totals =	$954.25		$1,032.1544	$1,032.15	$1,032.20	$1,032.20