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	$162.39	3.556%	$168.1646	$168.16	$168.15	$168.20
Purchase #2	$25.59	8.325%	$27.7204	$27.72	$27.70	$27.70
Purchase #3	$172.79	5.516%	$182.3211	$182.32	$182.30	$182.30
Purchase #4	$61.38	10.735%	$67.9691	$67.97	$67.95	$68.00
Purchase #5	$181.75	5.526%	$191.7935	$191.79	$191.80	$191.80
Purchase #6	$85.76	12.848%	$96.7784	$96.78	$96.80	$96.80
Purchase #7	$124.37	7.367%	$133.5323	$133.53	$133.55	$133.50
7 purchase totals =	$814.03		$868.2794	$868.27	$868.25	$868.30