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	$74.87	10.261%	$82.5524	$82.55	$82.55	$82.60
Purchase #2	$195.47	13.261%	$221.3913	$221.39	$221.40	$221.40
Purchase #3	$148.70	10.331%	$164.0622	$164.06	$164.05	$164.10
Purchase #4	$98.68	5.167%	$103.7788	$103.78	$103.80	$103.80
Purchase #5	$95.97	4.128%	$99.9316	$99.93	$99.95	$99.90
Purchase #6	$163.27	10.867%	$181.0126	$181.01	$181.00	$181.00
Purchase #7	$157.81	10.810%	$174.8693	$174.87	$174.85	$174.90
7 purchase totals =	$934.77		$1,027.5982	$1,027.59	$1,027.60	$1,027.70