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	$224.48	11.151%	$249.5118	$249.51	$249.50	$249.50
Purchase #2	$106.56	7.547%	$114.6021	$114.60	$114.60	$114.60
Purchase #3	$49.72	9.592%	$54.4891	$54.49	$54.50	$54.50
Purchase #4	$36.92	11.471%	$41.1551	$41.16	$41.15	$41.20
Purchase #5	$59.62	12.842%	$67.2764	$67.28	$67.30	$67.30
Purchase #6	$134.70	13.380%	$152.7229	$152.72	$152.70	$152.70
Purchase #7	$87.64	11.377%	$97.6108	$97.61	$97.60	$97.60
7 purchase totals =	$699.64		$777.3682	$777.37	$777.35	$777.40