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	$51.91	4.128%	$54.0528	$54.05	$54.05	$54.10
Purchase #2	$72.45	8.292%	$78.4576	$78.46	$78.45	$78.50
Purchase #3	$174.47	10.523%	$192.8295	$192.83	$192.85	$192.80
Purchase #4	$229.86	8.291%	$248.9177	$248.92	$248.90	$248.90
Purchase #5	$153.90	3.398%	$159.1295	$159.13	$159.15	$159.10
Purchase #6	$181.59	9.835%	$199.4494	$199.45	$199.45	$199.40
Purchase #7	$159.64	8.315%	$172.9141	$172.91	$172.90	$172.90
7 purchase totals =	$1,023.82		$1,105.7506	$1,105.75	$1,105.75	$1,105.70