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	$34.40	9.257%	$37.5844	$37.58	$37.60	$37.60
Purchase #2	$245.55	4.443%	$256.4598	$256.46	$256.45	$256.50
Purchase #3	$181.56	6.162%	$192.7477	$192.75	$192.75	$192.70
Purchase #4	$217.72	10.170%	$239.8621	$239.86	$239.85	$239.90
Purchase #5	$143.27	12.273%	$160.8535	$160.85	$160.85	$160.90
Purchase #6	$188.51	12.646%	$212.349	$212.35	$212.35	$212.30
Purchase #7	$67.60	4.326%	$70.5244	$70.52	$70.50	$70.50
7 purchase totals =	$1,078.61		$1,170.3809	$1,170.37	$1,170.35	$1,170.40