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	$186.25	12.249%	$209.0638	$209.06	$209.05	$209.10
Purchase #2	$138.53	4.592%	$144.8913	$144.89	$144.90	$144.90
Purchase #3	$166.29	13.609%	$188.9204	$188.92	$188.90	$188.90
Purchase #4	$207.85	10.303%	$229.2648	$229.26	$229.25	$229.30
Purchase #5	$31.50	12.339%	$35.3868	$35.39	$35.40	$35.40
Purchase #6	$105.65	10.828%	$117.0898	$117.09	$117.10	$117.10
Purchase #7	$78.62	9.208%	$85.8593	$85.86	$85.85	$85.90
7 purchase totals =	$914.69		$1,010.4762	$1,010.47	$1,010.45	$1,010.60