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	$92.98	11.627%	$103.7908	$103.79	$103.80	$103.80
Purchase #2	$79.50	3.341%	$82.1561	$82.16	$82.15	$82.20
Purchase #3	$36.49	13.608%	$41.4556	$41.46	$41.45	$41.50
Purchase #4	$129.51	5.354%	$136.444	$136.44	$136.45	$136.40
Purchase #5	$211.94	10.213%	$233.5854	$233.59	$233.60	$233.60
Purchase #6	$250.85	11.213%	$278.9778	$278.98	$279.00	$279.00
Purchase #7	$144.65	5.535%	$152.6564	$152.66	$152.65	$152.70
7 purchase totals =	$945.92		$1,029.0661	$1,029.08	$1,029.10	$1,029.20