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	$190.82	5.268%	$200.8724	$200.87	$200.85	$200.90
Purchase #2	$74.78	13.866%	$85.149	$85.15	$85.15	$85.10
Purchase #3	$38.98	10.247%	$42.9743	$42.97	$42.95	$43.00
Purchase #4	$85.33	4.804%	$89.4293	$89.43	$89.45	$89.40
Purchase #5	$92.53	3.176%	$95.4688	$95.47	$95.45	$95.50
Purchase #6	$141.80	13.198%	$160.5148	$160.51	$160.50	$160.50
Purchase #7	$167.81	3.110%	$173.0289	$173.03	$173.05	$173.00
7 purchase totals =	$792.05		$847.4375	$847.43	$847.40	$847.40