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	$227.29	8.857%	$247.4211	$247.42	$247.40	$247.40
Purchase #2	$64.95	11.228%	$72.2426	$72.24	$72.25	$72.20
Purchase #3	$68.67	8.191%	$74.2948	$74.29	$74.30	$74.30
Purchase #4	$75.35	4.563%	$78.7882	$78.79	$78.80	$78.80
Purchase #5	$121.32	9.462%	$132.7993	$132.80	$132.80	$132.80
Purchase #6	$209.38	4.574%	$218.957	$218.96	$218.95	$219.00
Purchase #7	$64.27	13.399%	$72.8815	$72.88	$72.90	$72.90
7 purchase totals =	$831.23		$897.3845	$897.38	$897.40	$897.40