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	$192.51	3.660%	$199.5559	$199.56	$199.55	$199.60
Purchase #2	$94.64	11.414%	$105.4422	$105.44	$105.45	$105.40
Purchase #3	$191.47	12.722%	$215.8288	$215.83	$215.85	$215.80
Purchase #4	$226.65	12.583%	$255.1694	$255.17	$255.15	$255.20
Purchase #5	$180.98	4.789%	$189.6471	$189.65	$189.65	$189.60
Purchase #6	$46.90	11.615%	$52.3474	$52.35	$52.35	$52.30
Purchase #7	$163.49	9.205%	$178.5393	$178.54	$178.55	$178.50
7 purchase totals =	$1,096.64		$1,196.5301	$1,196.54	$1,196.55	$1,196.40