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	$43.81	11.550%	$48.8701	$48.87	$48.85	$48.90
Purchase #2	$244.64	9.450%	$267.7585	$267.76	$267.75	$267.80
Purchase #3	$178.86	9.806%	$196.399	$196.40	$196.40	$196.40
Purchase #4	$175.86	5.628%	$185.7574	$185.76	$185.75	$185.80
Purchase #5	$163.53	3.390%	$169.0737	$169.07	$169.05	$169.10
Purchase #6	$169.46	6.826%	$181.0273	$181.03	$181.05	$181.00
Purchase #7	$69.56	12.255%	$78.0846	$78.08	$78.10	$78.10
7 purchase totals =	$1,045.72		$1,126.9706	$1,126.97	$1,126.95	$1,127.10