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	$95.59	9.749%	$104.9091	$104.91	$104.90	$104.90
Purchase #2	$110.95	5.837%	$117.4262	$117.43	$117.45	$117.40
Purchase #3	$42.30	10.191%	$46.6108	$46.61	$46.60	$46.60
Purchase #4	$181.78	9.716%	$199.4417	$199.44	$199.45	$199.40
Purchase #5	$166.31	6.357%	$176.8823	$176.88	$176.90	$176.90
Purchase #6	$111.51	3.307%	$115.1976	$115.20	$115.20	$115.20
Purchase #7	$234.89	12.131%	$263.3845	$263.38	$263.40	$263.40
7 purchase totals =	$943.33		$1,023.8522	$1,023.85	$1,023.90	$1,023.80