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	$151.36	11.553%	$168.8466	$168.85	$168.85	$168.80
Purchase #2	$25.38	3.662%	$26.3094	$26.31	$26.30	$26.30
Purchase #3	$79.70	3.563%	$82.5397	$82.54	$82.55	$82.50
Purchase #4	$17.27	12.312%	$19.3963	$19.40	$19.40	$19.40
Purchase #5	$70.81	11.462%	$78.9262	$78.93	$78.95	$78.90
Purchase #6	$92.82	11.616%	$103.602	$103.60	$103.60	$103.60
Purchase #7	$88.78	12.548%	$99.9201	$99.92	$99.90	$99.90
7 purchase totals =	$526.12		$579.5403	$579.55	$579.55	$579.40