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	$40.97	4.869%	$42.9648	$42.96	$42.95	$43.00
Purchase #2	$53.81	7.255%	$57.7139	$57.71	$57.70	$57.70
Purchase #3	$95.85	4.268%	$99.9409	$99.94	$99.95	$99.90
Purchase #4	$175.77	3.342%	$181.6442	$181.64	$181.65	$181.60
Purchase #5	$11.78	5.586%	$12.438	$12.44	$12.45	$12.40
Purchase #6	$81.29	4.739%	$85.1423	$85.14	$85.15	$85.10
Purchase #7	$41.99	6.494%	$44.7168	$44.72	$44.70	$44.70
7 purchase totals =	$501.46		$524.5609	$524.55	$524.55	$524.40