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	$86.64	6.789%	$92.522	$92.52	$92.50	$92.50
Purchase #2	$95.73	6.420%	$101.8759	$101.88	$101.90	$101.90
Purchase #3	$158.57	5.839%	$167.8289	$167.83	$167.85	$167.80
Purchase #4	$183.43	3.577%	$189.9913	$189.99	$190.00	$190.00
Purchase #5	$17.32	6.178%	$18.39	$18.39	$18.40	$18.40
Purchase #6	$125.42	5.805%	$132.7006	$132.70	$132.70	$132.70
Purchase #7	$56.51	5.383%	$59.5519	$59.55	$59.55	$59.60
7 purchase totals =	$723.62		$762.8606	$762.86	$762.90	$762.90