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	$240.85	10.114%	$265.2096	$265.21	$265.20	$265.20
Purchase #2	$77.50	6.690%	$82.6848	$82.68	$82.70	$82.70
Purchase #3	$104.89	10.813%	$116.2318	$116.23	$116.25	$116.20
Purchase #4	$95.85	8.169%	$103.68	$103.68	$103.70	$103.70
Purchase #5	$66.87	5.196%	$70.3446	$70.34	$70.35	$70.30
Purchase #6	$50.65	5.758%	$53.5664	$53.57	$53.55	$53.60
Purchase #7	$145.30	7.688%	$156.4707	$156.47	$156.45	$156.50
7 purchase totals =	$781.91		$848.1879	$848.18	$848.20	$848.20