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	$142.70	3.870%	$148.2225	$148.22	$148.20	$148.20
Purchase #2	$15.57	9.225%	$17.0063	$17.01	$17.00	$17.00
Purchase #3	$119.81	3.153%	$123.5876	$123.59	$123.60	$123.60
Purchase #4	$184.32	7.332%	$197.8343	$197.83	$197.85	$197.80
Purchase #5	$189.85	3.152%	$195.8341	$195.83	$195.85	$195.80
Purchase #6	$140.71	8.411%	$152.5451	$152.55	$152.55	$152.50
Purchase #7	$106.56	4.256%	$111.0952	$111.10	$111.10	$111.10
7 purchase totals =	$899.52		$946.1251	$946.13	$946.15	$946.00