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	$144.48	9.782%	$158.613	$158.61	$158.60	$158.60
Purchase #2	$106.31	5.344%	$111.9912	$111.99	$112.00	$112.00
Purchase #3	$67.40	7.206%	$72.2568	$72.26	$72.25	$72.30
Purchase #4	$116.59	9.725%	$127.9284	$127.93	$127.95	$127.90
Purchase #5	$140.29	5.385%	$147.8446	$147.84	$147.85	$147.80
Purchase #6	$67.70	5.605%	$71.4946	$71.49	$71.50	$71.50
Purchase #7	$177.98	5.648%	$188.0323	$188.03	$188.05	$188.00
7 purchase totals =	$820.75		$878.1609	$878.15	$878.20	$878.10