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	$142.76	12.763%	$160.9805	$160.98	$161.00	$161.00
Purchase #2	$164.41	9.645%	$180.2673	$180.27	$180.25	$180.30
Purchase #3	$137.48	5.733%	$145.3617	$145.36	$145.35	$145.40
Purchase #4	$100.99	8.819%	$109.8963	$109.90	$109.90	$109.90
Purchase #5	$85.38	6.411%	$90.8537	$90.85	$90.85	$90.90
Purchase #6	$174.50	4.244%	$181.9058	$181.91	$181.90	$181.90
Purchase #7	$56.55	12.809%	$63.7935	$63.79	$63.80	$63.80
7 purchase totals =	$862.07		$933.0588	$933.06	$933.05	$933.20