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	$186.33	13.670%	$211.8013	$211.80	$211.80	$211.80
Purchase #2	$175.38	13.545%	$199.1352	$199.14	$199.15	$199.10
Purchase #3	$127.47	8.526%	$138.3381	$138.34	$138.35	$138.30
Purchase #4	$168.46	7.825%	$181.642	$181.64	$181.65	$181.60
Purchase #5	$80.71	5.854%	$85.4348	$85.43	$85.45	$85.40
Purchase #6	$243.78	11.506%	$271.8293	$271.83	$271.85	$271.80
Purchase #7	$104.43	12.654%	$117.6446	$117.64	$117.65	$117.60
7 purchase totals =	$1,086.56		$1,205.8253	$1,205.82	$1,205.90	$1,205.60