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	$99.71	8.643%	$108.3279	$108.33	$108.35	$108.30
Purchase #2	$148.98	11.591%	$166.2483	$166.25	$166.25	$166.20
Purchase #3	$235.81	10.286%	$260.0654	$260.07	$260.05	$260.10
Purchase #4	$37.88	12.252%	$42.5211	$42.52	$42.50	$42.50
Purchase #5	$74.48	5.141%	$78.309	$78.31	$78.30	$78.30
Purchase #6	$148.91	10.522%	$164.5783	$164.58	$164.60	$164.60
Purchase #7	$217.97	3.391%	$225.3614	$225.36	$225.35	$225.40
7 purchase totals =	$963.74		$1,045.4114	$1,045.42	$1,045.40	$1,045.40