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	$144.90	10.600%	$160.2594	$160.26	$160.25	$160.30
Purchase #2	$173.70	4.617%	$181.7197	$181.72	$181.70	$181.70
Purchase #3	$106.79	9.131%	$116.541	$116.54	$116.55	$116.50
Purchase #4	$62.72	13.629%	$71.2681	$71.27	$71.25	$71.30
Purchase #5	$239.62	10.609%	$265.0413	$265.04	$265.05	$265.00
Purchase #6	$23.60	6.600%	$25.1576	$25.16	$25.15	$25.20
Purchase #7	$115.55	13.769%	$131.4601	$131.46	$131.45	$131.50
7 purchase totals =	$866.88		$951.4472	$951.45	$951.40	$951.50