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	$209.56	13.833%	$238.5484	$238.55	$238.55	$238.50
Purchase #2	$249.63	7.145%	$267.4661	$267.47	$267.45	$267.50
Purchase #3	$103.52	9.789%	$113.6536	$113.65	$113.65	$113.70
Purchase #4	$51.60	10.181%	$56.8534	$56.85	$56.85	$56.90
Purchase #5	$59.78	12.410%	$67.1987	$67.20	$67.20	$67.20
Purchase #6	$171.97	8.624%	$186.8007	$186.80	$186.80	$186.80
Purchase #7	$91.72	11.597%	$102.3568	$102.36	$102.35	$102.40
7 purchase totals =	$937.78		$1,032.8777	$1,032.88	$1,032.85	$1,033.00