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	$171.86	11.623%	$191.8353	$191.84	$191.85	$191.80
Purchase #2	$134.77	11.348%	$150.0637	$150.06	$150.05	$150.10
Purchase #3	$240.86	5.850%	$254.9503	$254.95	$254.95	$255.00
Purchase #4	$92.32	8.864%	$100.5032	$100.50	$100.50	$100.50
Purchase #5	$215.76	5.119%	$226.8048	$226.80	$226.80	$226.80
Purchase #6	$250.54	10.734%	$277.433	$277.43	$277.45	$277.40
Purchase #7	$46.74	11.362%	$52.0506	$52.05	$52.05	$52.10
7 purchase totals =	$1,152.85		$1,253.6409	$1,253.63	$1,253.65	$1,253.70