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	$152.64	4.693%	$159.8034	$159.80	$159.80	$159.80
Purchase #2	$82.32	4.354%	$85.9042	$85.90	$85.90	$85.90
Purchase #3	$108.64	13.844%	$123.6801	$123.68	$123.70	$123.70
Purchase #4	$119.27	3.605%	$123.5697	$123.57	$123.55	$123.60
Purchase #5	$235.42	9.866%	$258.6465	$258.65	$258.65	$258.60
Purchase #6	$241.34	6.562%	$257.1767	$257.18	$257.20	$257.20
Purchase #7	$117.57	13.488%	$133.4278	$133.43	$133.45	$133.40
7 purchase totals =	$1,057.20		$1,142.2084	$1,142.21	$1,142.25	$1,142.20