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	$165.54	10.855%	$183.5094	$183.51	$183.50	$183.50
Purchase #2	$102.36	12.762%	$115.4232	$115.42	$115.40	$115.40
Purchase #3	$61.80	8.849%	$67.2687	$67.27	$67.25	$67.30
Purchase #4	$238.84	10.799%	$264.6323	$264.63	$264.65	$264.60
Purchase #5	$216.93	11.547%	$241.9789	$241.98	$242.00	$242.00
Purchase #6	$226.72	3.136%	$233.8299	$233.83	$233.85	$233.80
Purchase #7	$244.45	13.666%	$277.8565	$277.86	$277.85	$277.90
7 purchase totals =	$1,256.64		$1,384.4989	$1,384.50	$1,384.50	$1,384.50