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	$148.82	4.847%	$156.0333	$156.03	$156.05	$156.00
Purchase #2	$20.86	4.634%	$21.8267	$21.83	$21.85	$21.80
Purchase #3	$165.78	7.603%	$178.3843	$178.38	$178.40	$178.40
Purchase #4	$51.88	3.286%	$53.5848	$53.58	$53.60	$53.60
Purchase #5	$166.64	4.139%	$173.5372	$173.54	$173.55	$173.50
Purchase #6	$100.41	8.122%	$108.5653	$108.57	$108.55	$108.60
Purchase #7	$225.53	9.131%	$246.1231	$246.12	$246.10	$246.10
7 purchase totals =	$879.92		$938.0547	$938.05	$938.10	$938.00