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	$223.48	13.677%	$254.0454	$254.05	$254.05	$254.00
Purchase #2	$103.66	3.642%	$107.4353	$107.44	$107.45	$107.40
Purchase #3	$42.93	13.844%	$48.8732	$48.87	$48.85	$48.90
Purchase #4	$179.98	9.141%	$196.432	$196.43	$196.45	$196.40
Purchase #5	$179.93	11.230%	$200.1361	$200.14	$200.15	$200.10
Purchase #6	$52.29	13.675%	$59.4407	$59.44	$59.45	$59.40
Purchase #7	$114.78	5.303%	$120.8668	$120.87	$120.85	$120.90
7 purchase totals =	$897.05		$987.2295	$987.24	$987.25	$987.10