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	$82.28	3.757%	$85.3713	$85.37	$85.35	$85.40
Purchase #2	$63.50	12.670%	$71.5455	$71.55	$71.55	$71.50
Purchase #3	$250.70	4.539%	$262.0793	$262.08	$262.10	$262.10
Purchase #4	$29.92	13.444%	$33.9424	$33.94	$33.95	$33.90
Purchase #5	$59.63	12.139%	$66.8685	$66.87	$66.85	$66.90
Purchase #6	$74.83	11.586%	$83.4998	$83.50	$83.50	$83.50
Purchase #7	$20.65	10.697%	$22.8589	$22.86	$22.85	$22.90
7 purchase totals =	$581.51		$626.1657	$626.17	$626.15	$626.20