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	$194.70	13.307%	$220.6087	$220.61	$220.60	$220.60
Purchase #2	$146.69	9.305%	$160.3395	$160.34	$160.35	$160.30
Purchase #3	$155.33	9.155%	$169.5505	$169.55	$169.55	$169.60
Purchase #4	$211.71	3.852%	$219.8651	$219.87	$219.85	$219.90
Purchase #5	$95.30	7.377%	$102.3303	$102.33	$102.35	$102.30
Purchase #6	$127.48	11.830%	$142.5609	$142.56	$142.55	$142.60
Purchase #7	$66.85	5.151%	$70.2934	$70.29	$70.30	$70.30
7 purchase totals =	$998.06		$1,085.5484	$1,085.55	$1,085.55	$1,085.60