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	$124.34	10.735%	$137.6879	$137.69	$137.70	$137.70
Purchase #2	$162.78	6.792%	$173.836	$173.84	$173.85	$173.80
Purchase #3	$115.56	6.526%	$123.1014	$123.10	$123.10	$123.10
Purchase #4	$142.58	9.453%	$156.0581	$156.06	$156.05	$156.10
Purchase #5	$61.95	7.765%	$66.7604	$66.76	$66.75	$66.80
Purchase #6	$163.37	4.784%	$171.1856	$171.19	$171.20	$171.20
Purchase #7	$174.98	8.370%	$189.6258	$189.63	$189.65	$189.60
7 purchase totals =	$945.56		$1,018.2552	$1,018.27	$1,018.30	$1,018.30