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	$172.82	13.492%	$196.1369	$196.14	$196.15	$196.10
Purchase #2	$65.42	7.117%	$70.0759	$70.08	$70.10	$70.10
Purchase #3	$82.45	3.502%	$85.3374	$85.34	$85.35	$85.30
Purchase #4	$17.28	5.742%	$18.2722	$18.27	$18.25	$18.30
Purchase #5	$166.55	9.715%	$182.7303	$182.73	$182.75	$182.70
Purchase #6	$90.49	8.401%	$98.0921	$98.09	$98.10	$98.10
Purchase #7	$123.83	6.562%	$131.9557	$131.96	$131.95	$132.00
7 purchase totals =	$718.84		$782.6005	$782.61	$782.65	$782.60