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	$218.94	4.359%	$228.4836	$228.48	$228.50	$228.50
Purchase #2	$97.51	11.757%	$108.9743	$108.97	$108.95	$109.00
Purchase #3	$176.59	4.339%	$184.2522	$184.25	$184.25	$184.30
Purchase #4	$205.74	10.394%	$227.1246	$227.12	$227.10	$227.10
Purchase #5	$83.60	8.634%	$90.818	$90.82	$90.80	$90.80
Purchase #6	$37.41	12.860%	$42.2209	$42.22	$42.20	$42.20
Purchase #7	$204.28	11.555%	$227.8846	$227.88	$227.90	$227.90
7 purchase totals =	$1,024.07		$1,109.7582	$1,109.74	$1,109.70	$1,109.80