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	$123.57	7.303%	$132.5943	$132.59	$132.60	$132.60
Purchase #2	$98.98	12.197%	$111.0526	$111.05	$111.05	$111.10
Purchase #3	$82.65	3.141%	$85.246	$85.25	$85.25	$85.20
Purchase #4	$81.94	5.538%	$86.4778	$86.48	$86.50	$86.50
Purchase #5	$53.77	6.695%	$57.3699	$57.37	$57.35	$57.40
Purchase #6	$160.44	10.356%	$177.0552	$177.06	$177.05	$177.10
Purchase #7	$196.27	4.492%	$205.0864	$205.09	$205.10	$205.10
7 purchase totals =	$797.62		$854.8822	$854.89	$854.90	$855.00