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	$118.85	7.328%	$127.5593	$127.56	$127.55	$127.60
Purchase #2	$171.47	4.720%	$179.5634	$179.56	$179.55	$179.60
Purchase #3	$56.81	6.632%	$60.5776	$60.58	$60.60	$60.60
Purchase #4	$207.52	7.313%	$222.6959	$222.70	$222.70	$222.70
Purchase #5	$91.42	7.436%	$98.218	$98.22	$98.20	$98.20
Purchase #6	$78.46	5.303%	$82.6207	$82.62	$82.60	$82.60
Purchase #7	$194.85	4.833%	$204.2671	$204.27	$204.25	$204.30
7 purchase totals =	$919.38		$975.5020	$975.51	$975.45	$975.60