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	$205.58	6.661%	$219.2737	$219.27	$219.25	$219.30
Purchase #2	$47.39	7.812%	$51.0921	$51.09	$51.10	$51.10
Purchase #3	$114.40	12.409%	$128.5959	$128.60	$128.60	$128.60
Purchase #4	$82.39	3.458%	$85.239	$85.24	$85.25	$85.20
Purchase #5	$113.79	8.504%	$123.4667	$123.47	$123.45	$123.50
Purchase #6	$95.39	10.831%	$105.7217	$105.72	$105.70	$105.70
Purchase #7	$26.55	13.809%	$30.2163	$30.22	$30.20	$30.20
7 purchase totals =	$685.49		$743.6054	$743.61	$743.55	$743.60