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	$105.87	5.407%	$111.5944	$111.59	$111.60	$111.60
Purchase #2	$19.26	8.269%	$20.8526	$20.85	$20.85	$20.90
Purchase #3	$115.50	9.336%	$126.2831	$126.28	$126.30	$126.30
Purchase #4	$101.71	12.710%	$114.6373	$114.64	$114.65	$114.60
Purchase #5	$40.30	6.522%	$42.9284	$42.93	$42.95	$42.90
Purchase #6	$173.83	4.856%	$182.2712	$182.27	$182.25	$182.30
Purchase #7	$136.56	7.453%	$146.7378	$146.74	$146.75	$146.70
7 purchase totals =	$693.03		$745.3048	$745.30	$745.35	$745.30