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	$149.32	8.788%	$162.4422	$162.44	$162.45	$162.40
Purchase #2	$83.77	7.603%	$90.139	$90.14	$90.15	$90.10
Purchase #3	$210.59	12.769%	$237.4802	$237.48	$237.50	$237.50
Purchase #4	$219.37	7.349%	$235.4915	$235.49	$235.50	$235.50
Purchase #5	$175.47	10.157%	$193.2925	$193.29	$193.30	$193.30
Purchase #6	$101.98	9.801%	$111.9751	$111.98	$112.00	$112.00
Purchase #7	$243.62	4.289%	$254.0689	$254.07	$254.05	$254.10
7 purchase totals =	$1,184.12		$1,284.8894	$1,284.89	$1,284.95	$1,284.90