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	$101.66	3.828%	$105.5515	$105.55	$105.55	$105.60
Purchase #2	$205.45	12.226%	$230.5683	$230.57	$230.55	$230.60
Purchase #3	$224.87	11.429%	$250.5704	$250.57	$250.55	$250.60
Purchase #4	$165.56	9.607%	$181.4653	$181.47	$181.45	$181.50
Purchase #5	$135.59	11.754%	$151.5272	$151.53	$151.55	$151.50
Purchase #6	$131.34	10.703%	$145.3973	$145.40	$145.40	$145.40
Purchase #7	$200.85	6.713%	$214.3331	$214.33	$214.35	$214.30
7 purchase totals =	$1,165.32		$1,279.4131	$1,279.42	$1,279.40	$1,279.50