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	$99.52	10.167%	$109.6382	$109.64	$109.65	$109.60
Purchase #2	$116.60	9.134%	$127.2502	$127.25	$127.25	$127.30
Purchase #3	$118.35	5.461%	$124.8131	$124.81	$124.80	$124.80
Purchase #4	$218.45	4.816%	$228.9706	$228.97	$228.95	$229.00
Purchase #5	$241.59	7.504%	$259.7189	$259.72	$259.70	$259.70
Purchase #6	$19.71	7.710%	$21.2296	$21.23	$21.25	$21.20
Purchase #7	$158.42	7.345%	$170.0559	$170.06	$170.05	$170.10
7 purchase totals =	$972.64		$1,041.6765	$1,041.68	$1,041.65	$1,041.70