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	$108.59	9.471%	$118.8746	$118.87	$118.85	$118.90
Purchase #2	$52.86	9.477%	$57.8695	$57.87	$57.85	$57.90
Purchase #3	$248.78	6.591%	$265.1771	$265.18	$265.20	$265.20
Purchase #4	$140.52	8.654%	$152.6806	$152.68	$152.70	$152.70
Purchase #5	$174.78	4.304%	$182.3025	$182.30	$182.30	$182.30
Purchase #6	$53.97	10.499%	$59.6363	$59.64	$59.65	$59.60
Purchase #7	$91.69	10.670%	$101.4733	$101.47	$101.45	$101.50
7 purchase totals =	$871.19		$938.0139	$938.01	$938.00	$938.10