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	$106.41	4.754%	$111.4687	$111.47	$111.45	$111.50
Purchase #2	$126.63	5.292%	$133.3313	$133.33	$133.35	$133.30
Purchase #3	$105.67	10.223%	$116.4726	$116.47	$116.45	$116.50
Purchase #4	$100.35	6.211%	$106.5827	$106.58	$106.60	$106.60
Purchase #5	$209.91	8.567%	$227.893	$227.89	$227.90	$227.90
Purchase #6	$214.92	9.276%	$234.856	$234.86	$234.85	$234.90
Purchase #7	$113.91	5.116%	$119.7376	$119.74	$119.75	$119.70
7 purchase totals =	$977.80		$1,050.3419	$1,050.34	$1,050.35	$1,050.40