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	$49.45	9.528%	$54.1616	$54.16	$54.15	$54.20
Purchase #2	$135.75	11.140%	$150.8726	$150.87	$150.85	$150.90
Purchase #3	$10.43	12.394%	$11.7227	$11.72	$11.70	$11.70
Purchase #4	$226.55	4.464%	$236.6632	$236.66	$236.65	$236.70
Purchase #5	$240.77	6.679%	$256.851	$256.85	$256.85	$256.90
Purchase #6	$77.43	6.127%	$82.1741	$82.17	$82.15	$82.20
Purchase #7	$200.78	6.850%	$214.5334	$214.53	$214.55	$214.50
7 purchase totals =	$941.16		$1,006.9786	$1,006.96	$1,006.90	$1,007.10