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	$113.32	13.640%	$128.7768	$128.78	$128.80	$128.80
Purchase #2	$121.33	8.488%	$131.6285	$131.63	$131.65	$131.60
Purchase #3	$208.60	11.791%	$233.196	$233.20	$233.20	$233.20
Purchase #4	$128.98	13.144%	$145.9331	$145.93	$145.95	$145.90
Purchase #5	$98.35	8.650%	$106.8573	$106.86	$106.85	$106.90
Purchase #6	$217.43	10.388%	$240.0166	$240.02	$240.00	$240.00
Purchase #7	$74.32	8.716%	$80.7977	$80.80	$80.80	$80.80
7 purchase totals =	$962.33		$1,067.2060	$1,067.22	$1,067.25	$1,067.20