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	$105.84	5.271%	$111.4188	$111.42	$111.40	$111.40
Purchase #2	$74.86	13.828%	$85.2116	$85.21	$85.20	$85.20
Purchase #3	$61.98	12.213%	$69.5496	$69.55	$69.55	$69.50
Purchase #4	$138.37	9.748%	$151.8583	$151.86	$151.85	$151.90
Purchase #5	$40.41	5.287%	$42.5465	$42.55	$42.55	$42.50
Purchase #6	$232.85	11.591%	$259.8396	$259.84	$259.85	$259.80
Purchase #7	$138.84	10.187%	$152.9836	$152.98	$153.00	$153.00
7 purchase totals =	$793.15		$873.4080	$873.41	$873.40	$873.30