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	$131.83	4.866%	$138.2448	$138.24	$138.25	$138.20
Purchase #2	$155.92	8.234%	$168.7585	$168.76	$168.75	$168.80
Purchase #3	$40.79	3.628%	$42.2699	$42.27	$42.25	$42.30
Purchase #4	$17.58	10.822%	$19.4825	$19.48	$19.50	$19.50
Purchase #5	$156.28	7.607%	$168.1682	$168.17	$168.15	$168.20
Purchase #6	$40.75	9.658%	$44.6856	$44.69	$44.70	$44.70
Purchase #7	$158.49	11.314%	$176.4216	$176.42	$176.40	$176.40
7 purchase totals =	$701.64		$758.0311	$758.03	$758.00	$758.10