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	$52.52	8.190%	$56.8214	$56.82	$56.80	$56.80
Purchase #2	$185.79	13.557%	$210.9776	$210.98	$211.00	$211.00
Purchase #3	$54.86	5.467%	$57.8592	$57.86	$57.85	$57.90
Purchase #4	$221.77	9.697%	$243.275	$243.28	$243.30	$243.30
Purchase #5	$139.45	7.114%	$149.3705	$149.37	$149.35	$149.40
Purchase #6	$186.90	10.462%	$206.4535	$206.45	$206.45	$206.50
Purchase #7	$208.98	6.151%	$221.8344	$221.83	$221.85	$221.80
7 purchase totals =	$1,050.27		$1,146.5916	$1,146.59	$1,146.60	$1,146.70