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	$103.54	10.157%	$114.0566	$114.06	$114.05	$114.10
Purchase #2	$62.37	8.205%	$67.4875	$67.49	$67.50	$67.50
Purchase #3	$64.79	7.344%	$69.5482	$69.55	$69.55	$69.50
Purchase #4	$10.90	12.359%	$12.2471	$12.25	$12.25	$12.20
Purchase #5	$43.30	5.244%	$45.5707	$45.57	$45.55	$45.60
Purchase #6	$145.25	3.871%	$150.8726	$150.87	$150.85	$150.90
Purchase #7	$159.72	9.588%	$175.034	$175.03	$175.05	$175.00
7 purchase totals =	$589.87		$634.8167	$634.82	$634.80	$634.80