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	$93.56	11.518%	$104.3362	$104.34	$104.35	$104.30
Purchase #2	$106.95	12.293%	$120.0974	$120.10	$120.10	$120.10
Purchase #3	$149.97	11.486%	$167.1956	$167.20	$167.20	$167.20
Purchase #4	$95.82	9.188%	$104.6239	$104.62	$104.60	$104.60
Purchase #5	$137.69	4.418%	$143.7731	$143.77	$143.75	$143.80
Purchase #6	$33.72	11.264%	$37.5182	$37.52	$37.50	$37.50
Purchase #7	$238.64	10.146%	$262.8524	$262.85	$262.85	$262.90
7 purchase totals =	$856.35		$940.3968	$940.40	$940.35	$940.40